This article is dedicated to the M32 gearbox. It’s super common, so if you’ve ever owned a Vauxhall, Opel, Holden, Fiat, Alfa Romeo, Lotus, Lancia or Chevrolet you might have heard about the General Motors’ M32 transmission or maybe even had the displeasure to replace some gearbox bearings.

In this article, you will learn about the symptoms of bearing failure (which is what the M32 is known for), how to prevent it and how much it costs to fix an M32 gearbox that has already developed a problem.

M32 gearbox bearings

The weak point of the M32 gearbox is one of the two bearings that support the shaft with the 1st, 2nd, 5th and 6th gearwheels. This bearing is commonly called the “6th gear bearing” because it is located next to the 6th gear cogwheel, and also because the typical symptom of failure is the gearbox making a whining noise in 6th gear.

It’s difficult to say how long the original 6th gear bearing will last – some cars had issues as early as 30,000 miles and some vehicles make it to 130,000 miles before bearing failure. In my opinion, this is a fairly common problem. I think it’s likely that all M32 transmission will need to have the 6th gear bearing replaced at some point.

Personally, I’ve had two cars with the M32 gearbox, and both had bearings replaced at around 100,000 miles.

This is what a worn-out 6th gear bearing looks like:

Causes of bearing failure

Typically, the 6th gear bearing wears out first. However, there have been cases of other bearings failing as well. There are two things that cause bearing failure in the M32 gearboxes and both factors are connected.

Bearing size

The first and main reason for the problems with the M32 gearbox is the size of the bearings that hold the shafts inside the transmission. As I see it, they are simply too small.

The smaller the bearing surfaces, the higher the contact pressures between the rollers and the bearing surface (the M32 has tapered roller bearings). During normal operation, the rollers ride the oil film without touching the metal underneath. Higher contact pressures mean that the oil film that prevents the metal-to-metal contact is more likely to break.

So, if the contact pressures in the bearings become too high for the oil to handle, metal-to-metal contact will occur, and bearing material will start being worn away. I believe this is what happens in the M32 gearbox.

Highly stressed bearings are also more likely to experience metal fatigue. Metal fatigue in bearings is a type of failure where micro-cracks appear in the bearing components. The cracks can appear on the surface of the metal, or underneath. Both types of cracks lead to bearing material being removed from the bearing (peeling or flaking away).

It’s actually common to see fatigue wear on failed M32 bearings.

All evidence points towards bearings that are undersized for the conditions they operate in. Undersized bearings also stress the transmission oil, which leads us to the second factor that contributes to premature bearings wear in the M32 transmissions – the transmission oil itself.

Transmission oil

The second cause that contributes to bearing failure is the degradation of transmission oil. Old, degraded oil creates a weaker oil film that is more likely to break in high-stress situations. A good example of a high-stress situation is heavy acceleration in 6th gear during a long motorway run when the transmission is already hot.

Like most manual gearboxes, the M32 does not have an oil change interval specified in the service manual. It is assumed that the oil will last the “lifetime” of the vehicle. For many gearboxes, this works out fine.

So what makes many other gearboxes routinely reach 100,000 or 200,000 miles without oil changes and no symptoms of wear?

First of all, other gearboxes don’t have bearings made of chocolate. Second, the transmission oil has an easier life. One of the main factors that influence the useful lifespan of the oil is the operating temperature. 

The M32 does tend to run quite hot. It’s possible to see more than 125°C, which is hotter than the engine operating temperature. Such conditions change the oil viscosity over time and break down the additives that improve oil parameters.

Essentially, when the gearbox cooks the oil several times, it loses its lubricating properties, which leads to a weaker oil-film and accelerated wear.

As I already mentioned, the oil film is what prevents metal-to-metal contact between the gears and in the bearings. If the oil is not up to the task, things will start wearing out at an accelerated pace. The oil does have a tough job in the M32 gearbox, because of the highly-stressed bearings.

Basically, the M32 gearbox needs bigger bearings and fresh transmission oil! An oil cooler would be nice too…

Updated M32 gearboxes

The M32 gearbox was first used in 2004 in the Opel / Vauxhall Astra H. It took a while, but eventually General Motors made improvements to the gearbox to make the bearings last longer.

In the middle of 2012, General Motors gave the M32 transmission larger bearings and added oil galleries in the end case for better oil flow. The updated bearings are 62 mm in diameter, while the original ones were 55 mm. They are also much thicker (17.5 mm instead of 13.7 mm).

Pre-2012 gearboxes can be fitted with the larger bearings, provided that the updated end case is used.

After the 2012 update, these gearboxes should last much longer. If you are looking to buy a car with the M32 gearbox, definitely get one that was produced after 2012. Visually check that the car you are going to buy already has the updated end case. Not all cars had them immediately after the update.

The end case houses the problematic 6th gear bearing, and it’s just behind the front wheel on the left side of the car (UK’s passenger side). Here’s how you can distinguish the updated M32 gearbox from the previous model:

With the steering wheel turned all the way to the left, this is what you should see when you look through the gap between the front wheel arch and the front left wheel:

If you can’t see the gearbox this way, you will need to check from under the car. The M32 gearbox in the photo above obviously has the old type end case, but with new bearings and fresh transmission oil inside.

Luckily for me, I did not pay for the bearing replacement. The previous owner of the car did. This is one way to approach a problem like this. If you know what to look out for, you can buy a nice car with the major problems already fixed by someone else. Selfish? Yes, but don’t shoot the messenger. Better read my guide about buying used cars!

Okay, back to the M32 gearbox and its chocolate bearings.

Symptoms of a worn bearing

Below are the typical symptoms of the 6th gear bearing wear in the M32 gearbox:

• Whining noise in 6th and 5th gear. The noise may increase when you press the accelerator pedal and may decrease when you release it. Other gears may be noisy as well, but in the vast majority of cases, it’s just the last two gears.

• Gear stick movement in 1st and 5th gear when pressing/releasing the accelerator pedal. These gears share the same shaft, and the gear lever movement is caused by excess play in the worn-out “6th gear” bearing. It’s quite scary when you think about it – the shaft inside the transmission has enough play to move the gear lever.

• Bearing prison break – in severe cases, the 6th gear bearing may try to escape from the gearbox. If the bearing has worn out so much that it seizes, the outer bearing race can start spinning and grind a hole in the gearbox casing. That’s why it’s important to replace the bearings early enough. If left unattended, the end case may get damaged beyond repair.

If you are planning to buy a vehicle with the M32 transmission, definitely look out for the symptoms above. Check if the gearbox is quiet in all gears, and check if there is any movement of the gearstick when you press and release the accelerator pedal (in 1st and 5th gear).

Here’s what gear stick movement looks like:

And here’s what a worn-out gearbox bearing sounds like (not necessarily the 6th gear bearing):

Remember that the gearbox is near the left wheel, so that’s where the noise will be coming from.

M32 gearbox repair options

If the bearing wear is noticed early enough, the gearbox can be repaired by just fitting new bearings. It’s best to replace all the bearings that hold the input and output shafts (7 bearings in total). You can leave the differential bearings alone.

This is still much cheaper than replacing the entire transmission. If you leave a worn-out 6th gear bearing unattended for too long, it may try to drill a hole in the end case.

Because these gearboxes are used in so many vehicles, you should have no problems finding a garage that’s able to replace the bearings. You are also likely to find reconditioned gearboxes and repair kits online.

Replacing the bearings costs around £600 in an independent gearbox repair shop (all bearings except the differential). If you are looking at upgrading an old style M32 gearbox with the updated end case and new bearings, it would typically cost around £1000.

If you look on eBay, you will find that people sell “uprated” bearings that are supposed to last longer. Sadly, there is no such thing, unless we are talking about the larger 62mm bearings for 2012 and newer cars.

General Motors used a few suppliers (Timken, SNR, FAG, NGBC) and all bearings suffered the same faith. I don’t think that one is significantly better than the others. If anything, the Timken and SNR bearings may be slightly better than the other two.

The key to repairing the M32 transmission is to get the gearbox shimmed correctly when fitting new bearings. It’s important to have the bearings replaced at a reputable garage.

The tapered roller bearings need to be pre-tensioned correctly. This is done by using shims. Incorrect tension is likely to lead to yet another bearing replacement operation. So make sure that the people in the garage that’s going to repair your M32 gearbox know what they are doing.

M32 gearbox maintenance

There are a couple of things that you can do to improve the lifespan of your M32 transmission. The key thing is replacing the transmission oil regularly. No service interval is specified for the M32 (typical for manual boxes). However, I believe that it is essential if you want the M32 and its chocolate bearings to last.

I’ve heard people say that the original General Motors transmission oil is bad (GM 1940182). I don’t think that’s the reason why these gearboxes fail. GM’s oil is synthetic (good), and it was used in many other GM gearboxes, starting from the light-duty F13, up to the F40 that can handle 400 Nm. Other gearboxes that are filled with GM’s oil don’t have bearing issues.

The problem is that after 50,000 miles in the hot M32, the oil loses its properties and doesn’t offer the same protection as it did in the beginning. The same would apply to any other gear oil.

In 2012, along with the bearing upgrade, General Motors changed the oil to GM 1940004. This one is most likely better (why else would they change the oil?), but I don’t believe that the original GM oil is the cause of the problems.

If you’re still not convinced, Fiat and Alfa Romeo cars don’t use General Motors oil. They use Tutella Matryx. The M32 gearboxes in Fiat and Alfa Romeo cars fail all the same.

The bottom line is that you should pick a good synthetic oil and replace it every 30,000 miles. The newer General Motors oil will do fine, however, there are better options available.

Good:

• GM 1940004 75W-85 (General Motors factory fill since 2012)

• Tutela Matryx 75W-85 (Fiat & Alfa Romeo factory fill)

Better:

• Fuchs Sintofluid 75W-80 (recommended by many drivers and Vauxhall tuners, definitely the most popular uprated oil for the M32)

• Red Line MT-90 75W-90 (slightly thicker than 75W-85 – better for track cars or in hot climates)

Make sure the M32 gearbox is filled to a correct level (slightly overfilled is fine too). Underfilling the M32 gearbox is a recipe for bearing failure.

Another thing that you could do to prolong the life expectancy of the M32 gearbox bearings is to adjust your driving habits to avoid heavy acceleration in 6th and 5th gear to reduce the load on the 6th gear bearing. This is particularly important in diesel cars, which have a lot of torque.

M32 gearbox oil change

Manual gearboxes, including the M32, don’t have oil pumps to distribute the oil around the gears and bearings. They simply rely on the moving parts to splash the oil around (splash lubrication).

The shaft that holds the 1st, 2nd, 5th and 6th gearwheels is actually the one that’s mounted the lowest out of the three shafts. So the splashed oil will naturally flow down to the 6th gear bearing everytime the car is stopped.

If you’ve already browsed through internet forums in search of information about the M32 gearbox, you might have heard that overfilling the transmission makes it last longer because of improved lubrication of the 6th gear bearing.

Many people think that the 6th gear bearing is mounted somewhere in the upper part of the gearbox where the oil doesn’t reach. In reality, it’s mounted on the bottom, which is already the best place for a bearing to be. I think that adding more oil than specified by GM might help, but not for the reasons people mention.

Higher oil volume means that more heat can be absorbed, and I think this is the real reason why adding extra oil could help. Similarly, the oil channels added to the updated end case allow the oil to reach the bearings easier. The easier flow of oil through the bearings improves the heat transfer as well.

The oil capacity of the M32 gearbox is 2.4 litres. Filling it up to 2.8 litres is okay and may actually help. However, before you do anything, please double check what the correct oil quantity in your car should be.

2.4 litres is the common GM recommendation for the majority of cars with the M32 gearbox, however, they have recommended different quantities for some models.

Location of the oil plugs & how to change oil

The oil change procedure is as follows (you will need access to the underside of the car):

1. The oil fill plug is on top of the transmission, usually, right under the battery tray. In some cars, you can access the filler plug without removing the battery tray, for example, in the Fiat Bravo. In others, you will need to remove the battery and the battery tray. The filler plug is the first one that you should remove in case it’s stuck (you don’t want to drain the transmission and not be able to fill it back up).

   

2. Remove the drain plug, which is in the differential housing. Drain the oil for 10 minutes and put the drain plug back in. Tighten it to 20 Nm.

   

3. It’s not possible to drain all of the old oil and about 200 ml remains in the transmission. Therefore, you should add 2.2 litres of fresh oil or up to 2.6 litres if you prefer to overfill the gearbox slightly.

4. Put the filler plug back in (30 Nm), and reassemble the battery tray. Connect the battery.

5. Please note that the oil level plug remains untouched. If you remove the oil level plug, you won’t be able to fill the gearbox to more than 2.3 litres. Not using the oil level plug is the correct way to replace transmission oil in the M32. In fact, the updated (post-2012) M32 gearboxes don’t even have the oil level plug anymore.

Engine remapping & the M32

The M32 is rated at 320 Nm, however, there are many cars that are tuned well beyond this figure without an immediate impact on the gearbox operation (when not abused). There are diesel cars out there remapped to 400 Nm and these gearboxes can handle that when the bearings are in good condition.

Obviously, remapping the engine is not good for the gearbox bearings, but you may get away with it if you’re careful:

• Accept that the bearing lifespan may take a hit in remapped diesel cars. This is more likely for pre-2012 cars that have the 55mm bearings.

• Don’t use full engine torque in 6th gear.

• Use a top-quality gearbox oil and replace it regularly.

• Do not remap a car that’s already showing symptoms of bearing wear.

Buying a car with the M32 gearbox

The safest option is to find a car with the updated gearbox (2012 and newer cars).

When doing the pre-purchase inspection, pay attention to any noises and movement of the gear change lever. Drive the car and look out for the symptoms of bad bearings. If everything is fine, you can go ahead and buy the car. Once you get it, replace the transmission oil, and you should be just fine.

As for the pre-2012 cars, pay extra attention to any signs of bearing failure. Again, if everything is okay, you can buy the car, replace the gear oil and you should be fine for quite some time. Bearings don’t go bad overnight. Just remember to replace the transmission fluid regularly.

Buying a car that already had the bearings replaced (at a reputable car garage, with a receipt to prove) is also a great scenario.

Now, if you test-drive a car that’s showing symptoms of bearing wear, you can try to knock £600 off the car price. You can even show the owner this website! Regardless of whether you can negotiate the price down or not, you will need to replace the bearings before the end case gets damaged if you do decide to buy that particular car.

I recommend that you avoid cars that have very noisy bearings and a twitchy gear lever. In these cases, replacing the bearings might not be enough, which makes it a more expensive affair.

M20 gearbox

You may have come here to read about the M20 and not the M32 transmission. Actually, they are almost identical.

The M20 gearbox is a lower torque variant of the M32. The M20 is rated at 200 Nm and is mainly used with small diesel engines like the 1.3 Multijet/CDTi.

It suffers from the same problems as the M32, so everything here applies to the M20 as well. I can’t tell for sure, but the M20 should be somewhat more reliable because it transfers less torque than the M32, while the bearings are the same.

Oh God, it’s everywhere!

Here’s a list of vehicles that were fitted the M32 or the M20 gearbox:

• Opel / Vauxhall / Holden

  • Astra H (1.6 Turbo, 2.0 Turbo 1.3 CDTi, 1.7 CDTi, 1.9 CDTi)

  • Astra J (1.4 Turbo, 1.6 Turbo, 1.6 SIDI Turbo, 1.6 CDTi, 1.7 CDTi)

  • Astra K

  • Cascada

  • Vectra C

  • Signum

  • Insignia A (1.4 Turbo, 1.6, 1.6 Turbo, 1.6. SIDI Turbo, 1.8, 1.6 CDTi, 2.0 CDTi)

  • Insignia B

  • Zafira B (2.0 Turbo, 2.2 Direct Ecotec, 1.7 CDTi, 1.9 CDTi)

  • Zafira Tourer C

  • Zafira Tourer

  • Meriva A

  • Meriva B (1.4 Turbo, 1.6 CDTi, 1.7 CDTi)

  • Mokka

  • Corsa D (1.6 Turbo, 1.3 CDTi, 1.7 CDTi)

  • Corsa E

  • Adam

• Fiat

  • Grande Punto (1.3 MultiJet, 1.6 MultiJet, 1.9 MultiJet, Abarth 1.4 T-Jet)

  • Punto Evo (1.3 MultiJet Dualogic)

  • Bravo (1.4 T-Jet)

  • Croma

• Alfa Romeo

  • 159 (1.75 TBi, 1.9 JTS, 2.2 JTS, 1.9 JTDm 8v, 1.9 JTDm 16v)

  • Brera (1.75 TBi, 2.2 JTS)

  • Mito (1.4 TB 16v [155 PS only], 1.3 JTDm [90 PS only] and 1.6 JTDm until 2010)

• Lancia

  • Delta III

• Lotus

  • Europa

• Chevrolet

  • Cruze

  • Sonic

I think I’ve got all the European cars on this list, but I might have missed some Chevy models and other non-European cars. If you know something I don’t, please let me know in the comments!

M32 technical details

To finish this article, here’s some technical data, which may be useful to you.

As you now know, the M32 gearboxes are very common, and these are some of the reasons why they are so popular:

• It’s a relatively lightweight transmission. It weighs 41.5 kg without the transmission oil, and it is capable of transmitting 320 Nm of torque. For comparison, the General Motors F40 weighs 56.2kg and can handle 400 Nm. That’s almost 15 kg more for additional 80Nm of torque.

• It’s a three-shaft design, which makes it a compact gearbox. It’s only 33 cm long.

• The transmission gear change quality is better than in older GM transmissions because of the improved synchronization system. The gear change “feel” is also better when compared to the F40 gearbox. However, this is subjective because the F40 already uses similar gear synchronizers.

• I believe that standardization is the fourth reason. As an engineer, I can tell you that it’s an ideal situation for a car manufacturer to use only a couple models of transmissions, rather than a dozen various types. General Motors was a huge company that owned multiple brands. Hence, the widespread use of the same components.

There were many variants of the M32 gearbox when it comes to individual gear ratios. However, there were only five variants of the final drive ratios: 3.35, 3.65, 3.84, 3.94 and 4.18.

The individual gear ratios are as follows:

Then, it’s a pick-and-mix of final drive ratios and gearsets. Together, there are over 15 combinations.

As a final note, cars with the M20 or the M32 gearboxes always have dual-mass flywheels.

I hope you found this article useful.

If you’d like to read more about car transmission maintenance, follow this link.

The post M32 Gearbox: Chocolate Bearings appeared first on Still Running Strong.

This general car maintenance schedule was created to give you an idea what the typical maintenance items are and how often they need to be replaced – by mileage or time. This is an “average” maintenance schedule so it doesn’t apply to any car in particular.

For exact instructions regarding your car, you should consult your car owner’s manual. Please don’t exceed the intervals specified there.

You may not find service intervals for things like “fill for life” fluids in your car owner’s manual. “Lifetime” or “Sealed for life” is the assumption that the original fluid will last the lifespan of the vehicle, and the manufacturer doesn’t specify a service interval.

The decision whether to replace such fluids depends on you, more precisely, how long you want your car to last. I will explain more below.

Engine oil change

The oil change interval can vary, depending on the manufacturer’s recommendations and the type of engine oil used. Usually, it’s between 5,000 and 20,000 miles.

These are the typical oil change intervals, based on the type of engine oil:

• long-life synthetic oil – up to 20,000 miles, every 24 months, not recommended

• synthetic oil – between 10,000 and 15,000 miles, yearly

• semi-synthetic oil – 10,000 miles, yearly

• mineral oil – 5,000 miles, every 6 months

In the old days, synthetic oil was not available. Therefore, it was common to change the engine oil every 3,000 or 5,000 miles. This isn’t necessary anymore because synthetic oil has much better chemical and high-temperature stability. It is also better at removing deposits and doesn’t gel as quickly as mineral oil.

The trend is towards increasing the intervals between oil changes. I think there are good reasons behind it (improved oil formulas and extensive testing, for example), but I believe it is also driven by marketing.

Extended oil change intervals reduce the maintenance costs on paper, which is attractive to new car buyers. Also, it’s great for fleet owners because it reduces costs and the number of service visits. It’s better for the environment too (but probably not for your engine).

I don’t think the manufacturers care if the engines or turbochargers last for 200,000 miles. They only need to last long enough to keep the first and maybe the second owner of the car happy. I simply don’t have faith in some of the manufacturer’s claims because it’s not in their interest for the cars to stay on the road too long.

I think that extended oil change intervals are fine for some cars. However, they are not a good idea in cars which:

• have a timing chain, which is lubricated by engine oil

• have a turbocharger, which generates a lot of heat

• mainly do short trips in the city

Conclusions

The 10,000 miles interval is a good universal guideline if you use a decent quality synthetic oil. Most modern engines should be able to go for 10k miles between oil changes without any problems. In my opinion, the engine oil should be changed yearly, regardless of the mileage, because oil degradation is a function of mileage and time.

Some cars that are hard on engine oil may need more frequent oil changes. Please do not go without changing oil longer than specified in your service manual. If it says every 5,000 miles, there’s probably a reason.

The 20,000 miles long-life interval should be fine for naturally aspirated engines that have a timing belt. This is an interval for motorway driving and not for cars with fancy auxiliary equipment that relies on engine oil, for example, variable valve lift systems etc.

Also, keep in mind that sticking to a long-life oil change interval requires a long-life oil filter and specific engine oil.

There’s one more thing – switching from dinosaur oil to synthetic oil in old, high-mileage cars may not be advised because the engine may develop leaks when filled with thinner synthetic oil, which is better at removing deposits. Also, worn-out engines may burn more oil after a switch to a thin synthetic oil.

Basically, switching from mineral 15W-40 oil to synthetic 5W-40 oil in old cars isn’t necessarily a good idea, despite the fact that synthetic oil is superior in pretty much every aspect.

Engine air filter replacement

The air filter should be changed every 20,000 – 30,000 miles. A good rule of thumb is to replace it with every second or third oil change. The interval for your car will be specified in the manual. If you live in dusty or polluted areas, you may need to replace the filter more often than typically.

The replacement interval specified by the manufacturer depends on the size of the filter – a larger filter, with more surface area, will last longer. The design of the intake duct and the airbox is also important.

In modern cars, the airflow through the filter element is usually against gravity and the airbox is designed in a way that dust, stones and other garbage entering the filter chamber don’t actually hit the filter element. Heavy particles, like stones, just settle down in the airbox.

The air filter is usually the single easiest maintenance item to replace. If you’d like to learn how to work on your car, this is a good DIY opportunity. In some cars, you may be able to do it in 60 seconds without any tools, in others it may take 10 minutes and you may need to use a regular screwdriver or a Torx screwdriver.

What are your experiences with changing the air filter? Let me know in the comments below. Let’s find the world’s worst air filter placement – one that makes changing the filter more than a 10-minute job.

Brake fluid (DOT3, DOT4, DOT5.1)

You should replace the brake fluid every two years, regardless of mileage. Brake fluid is hygroscopic, which means it absorbs moisture from the environment and becomes less resistant to high temperatures over time.

If the temperature of the brake fluid rises to the boiling point, gas bubbles will appear in the system and the brake pedal will go to the floor with little resistance and equally little braking force when you try to use the brakes. Replacing the brake fluid is especially important if you drive on mountain roads or you simply like to drive hard.

Another reason to change brake fluid regularly is that it may corrode the brake system if it’s contaminated with water and the corrosion inhibitors have degraded over time.

The most common brake fluid used in modern cars is DOT4. DOT4 can be mixed with the older DOT3 and the newer DOT5.1 as they are all glycol based. The DOT rating is related to the boiling temperature and the performance of the brake fluid. The higher the number, the better.

Although the fluids above can be mixed if need be, please use the brake fluid specified in your car owner’s manual.

There is also the silicone-based DOT5, which is a completely different animal and should never be mixed with glycol brake fluids. Again, please refer to your car owner’s manual.

Cabin air filter replacement

The cabin air filter should typically be changed every one or two years. In miles, it’s between 10,000 and 30,000. The interval is heavily dependent on the conditions (dust, pollution, pollen).

The cabin filter is often overlooked in used cars. When not replaced for too long, the air coming from the air vents may start smelling bad because of the bacterial growth within the organic matter in the filter (twigs, leaves, dead bugs).

These pollen filters can get really dirty, often quicker than engine air filters. Some filters have a sheet of activated carbon that eliminates bad smells. The activated carbon works only for as long as it’s not completely covered with dust.

The cabin filter may be more difficult to replace than the engine air filter because it’s usually in a more awkward location, for example, under the glove box. Still, replacing it is definitely within reach for someone with just basic DIY skills.

Automatic Transmission Fluid (ATF)

Typically, it should be changed not later than every 70,000 miles when using synthetic oil. Using the correct oil in your transmission is very important – it has to have the correct friction coefficient and viscosity to work well with the transmission clutch plates.

Now, let me clear something up. When it comes to automatic transmissions, there is no such thing as “filled for life”. ATF is not magical and does degrade just like any lubricant.

Over time, the friction modifiers break down, changing the transmission shifting characteristic. Also, the fluid oxidizes from the heat generated in the torque converter. Oxidized fluid won’t have the lubricating properties it used to, and there will be a change in its viscosity.

Then there is the abrasive debris generated by the clutch packs that will stay in the transmission unless removed with the fluid and the filter. Therefore, never changing the transmission fluid will accelerate the wear on the transmission.

Consider these two options:

1. The transmission oil is changed every 70,000 miles and the transmission is still running strong at 200,000 miles.

2. The transmission oil is never changed and the transmission fails at 120,000 miles. The original fluid lasted the “life” of the transmission, didn’t it? It’s a self-fulfilling prophecy.

The manufacturers don’t care if transmissions fail at 100k or 200k miles. At this point, the car is out of warranty and the first owner most likely sold the car already. In fact, it’s better if transmissions fail – there is money to be made servicing them and it creates an incentive to buy new vehicles.

As I see it, “sealed for life” means “as long as the warranty lasts”.

There is no doubt that modern, synthetic ATF has much better chemical stability and resistance to oxidation when compared to mineral-based ATF, which allows us to increase the time between oil changes.

The 70,000 miles interval I mentioned above is assuming you are already using synthetic ATF. If your vehicle is filled with mineral ATF, a reasonable interval would be about 40,000 miles. As always, don’t exceed the ATF replacement interval (if there is one) in your car owner’s manual. The intervals I mention here are just some reasonable examples.

A simple and safe method of changing the transmission fluid in used cars is to:

1. Drain as much old fluid as possible. Usually, about 50% or maybe 60% will come out, the rest will remain in the torque converter.

2. Fill up the transmission with fresh fluid and go for a drive. Let the transmission warm up and shift through the gears, then come back and drain it again.

3. Refill with fresh fluid again. If possible, change the transmission filter as well.

This way you can replace 80% of the old fluid without forcing the new fluid in under pressure as you would with a transmission flush. Remember to buy enough fluid for two drain/fill cycles.

I don’t recommend flushing the transmission in older cars as it’s an aggressive procedure which may cause issues in poorly serviced and worn-out transmissions.

Manual transmission fluid

It’s likely that your car owner’s manual does not specify a change interval for manual transmission fluid. As opposed to an automatic transmission, I could agree that a well designed manual gearbox can indeed live a very long life on the factory fill.

This is because there isn’t nearly as much heat generated in a manual gearbox – there is no torque converter and a lot less slipping occurs when changing gears. There are no valves which can get clogged with sludge or wear out from poor lubrication. Also, a lot less debris is generated because there are no clutch packs as the clutch is outside of the gearbox.

Still, the good practice is to replace the transmission fluid in manual gearboxes. Replacing it every 100k miles should be adequate as long as good quality synthetic oil is used. Flushing isn’t necessary.

In some cases, the oil change interval should be reduced, for example, when the car is used for towing or in heavy vehicles in general. Also, some gearboxes are simply weak and require dramatically more frequent gear oil changes to prevent premature wear.

Power steering fluid change

The power steering fluid is another item that may not have a replacement interval specified in the car owner’s manual. Just like with the manual gearbox oil, replacing the power steering fluid every 100k miles should be enough, in my opinion.

If it’s not specified in the manual, it’s up to you whether you want to replace it or not. The power steering fluid does degrade over time, and by 100k miles it will most likely be full of metal particles.

Engine coolant replacement

The coolant replacement interval depends on the type of antifreeze used. Here are the three major kinds of antifreeze used in cars:

• Inorganic Acid Technology (IAT coolant) – this is the classic green stuff that needs to be replaced every 2 or 3 years.

• Organic Acid Technology (OAT coolant) – this is a type of long-life coolant that typically lasts 5 years.

• Hybrid Organic Acid Technology (HOAT coolant) – this is the latest and most long-lived coolant type. The HOAT coolant replacement interval may exceed 5 years and typically it is up to 7 years.

As with most car fluids, using the correct type of coolant is important as IAT and OAT fluids don’t mix. Topping up with a random antifreeze is a bad idea – better add some distilled water until you can replace the entire fluid.

Over time, the coolant loses its rust-inhibiting properties and it may start corroding the cooling system internally. While the coolant will maintain it’s properties for quite long (i.e. it will not freeze), the corrosion inhibitors will be long gone before then. That’s why it’s important not to exceed the replacement intervals specified by the manufacturers.

Some manufacturers specify a “long-life” service interval for the engine coolant. For example, Mercedes-Benz specified a 15 years interval for some of their cars. They achieved this by adding a silica gel packet to the coolant reservoir. The chemistry of the coolant would not last that long on its own.

As I see it, the long-life intervals are fine as long as it’s not something ridiculous like 10+ years, unless there is some clever engineering involved. In most cases, a typical, non-OEM, long-life coolant is usually good for 5 or 7 years.

Coolant flushes are usually not necessary if the car has been maintained properly. Also, in older vehicles, flushing can expose weak points and make leaks show up.

Fuel filter replacement

Petrol engines – The petrol filter is usually located under the car near the fuel tank, or in the fuel tank itself in case of “lifetime” filters. The replacement intervals vary, it may be 50k miles, 100k miles or never when it’s a “lifetime” filter.

I think that ‘never’ is a bit optimistic for any kind of filter. Therefore, I recommend replacing the “lifetime” filters at 100,000 miles. Otherwise, please follow the instructions in your car owner’s manual.

Diesel engines – The diesel filter is usually located under the bonnet for easy access. That’s because it needs to be replaced a lot more often than a petrol filter. The diesel filter is typically replaced every 20,000 – 30,000 miles.

Just like with the air filter, a good rule of thumb is to replace it with every second or third oil change.

Modern diesel injection systems run at stupidly high pressures (1500 bar+) and the fuel must be very clean no to damage the pump or the injectors. As the filter ages, it gets clogged. This puts more strain on the fuel pump, which needs to work harder to pump the fuel. Therefore, it’s important to replace these filters on time.

Spark plug replacement

A spark plug is what ignites the air-fuel mixture in a petrol engine. There is usually one spark plug per cylinder, sometimes two. The type of material used for the spark plug electrodes determines the lifespan of the spark plug. The electrodes are the areas where the electrical arc is generated.

The typical spark plug replacement intervals are as follows:

• 30k miles for copper spark plugs. These are the cheapest kind. They are still often used in turbocharged engines.

• 70k miles for platinum spark plugs. These are typical long-life spark plugs found in modern cars.

• 100k miles for iridium spark plugs. These are the most corrosion resistant, longest lasting spark plugs. Iridium may be linked to the asteroid that killed the dinosaurs, but it’s great for spark plugs!

Oh, one more thing. Copper spark plugs don’t actually have copper electrodes. In reality, they have copper cores (like most spark plugs) and nickel electrodes. The correct name should be nickel spark plugs, but that’s not what people call them.

Worn-out spark plugs reduce mileage and power. Badly worn-out plugs can cause engine misfires. If you continue driving a car that misfires, you may damage (melt) the catalytic converter because of the unburnt fuel entering the exhaust.

Brake pads and discs

Brake pads and discs should be replaced as needed. Their wear is highly dependent on the driver.

If you have a mid-sized car and drive “normally”, the average lifespan of front brake pads should be around 50,000 miles while the rear pads may last 75,000 miles. On the other hand, if you drive like a maniac, you might need new pads even after 20,000 miles. Most of the braking force is applied to the front wheels so front brakes wear out faster.

It is recommended to replace the brake discs at the same time as the brake pads, but it isn’t always necessary. Brake discs become thinner as they wear, and manufacturers specify a minimum brake disc thickness.

You might be able to replace just the pads if the discs still have an adequate thickness and their surface is still good. Before deciding to replace the brake pads alone, consult a specialist to evaluate the condition of your brake discs.

Replacing tyres

Just like with the brake pads, tyre wear is highly dependent on the driver. The tyres should be replaced when they are worn out or when they get too old.

A minimum tyre tread depth is specified in most countries. In the UK, it’s 1.6mm for passenger cars. This should be measured across the central three-quarters of the tyre tread. The 1.6mm is a legal requirement, which is far from optimal. In my opinion, the tyres should be replaced earlier.

The usual recommendation is to replace the tyres when the tread wears below:

• 3mm for summer tyres

• 4mm for winter tyres (1.6mm is useless in snow)

For summer tyres, the braking distance on wet roads starts to increase dramatically below 3mm. You may expect a 30% increase in braking distance going from 3mm to 1.6mm tyre tread. For reference, new tyres usually start with around 8mm of tread.

As for the age of the tyre, 10 years is the maximum, in my opinion. That’s because the rubber degrades over time and becomes more susceptible to cracking. It’s also good to know that tyres in storage don’t degrade nearly as fast as when driving. Buying a brand new tyre that has been in storage for 3 years is not a big deal as long as it’s been stored properly. Tyres Are Not Bananas.

Lastly, other reasons to replace tyres include heavy uneven wear, sidewall bulges or large cracks.

The manufacturing date is stamped on the tyres so it’s easy to check their age. Here’s how:

The first two digits denote the week of production and the second two digits represent the year. Therefore, the tyre in the photo above was produced in the 49th week (November) of 2015.

If you found this article useful, please share it with your friends!

And get that 3-year-old cabin filter changed already…

The post Routine Car Maintenance Schedule appeared first on Still Running Strong.

This article will help you decide if a modern diesel car is a right choice for you. It may get technical at times. However, if you bear with me until the end, you will learn:

• why diesel engines are more efficient than petrol engines

• why diesel emissions became a problem for manufacturers and drivers

• what typically fails in diesel engines and how much it costs to fix

• if driving a diesel car makes sense for you

Diesel engine advantages

Modern diesel engines still operate on the same principle as 40 years ago. Diesel fuel is injected into the engine cylinders, and it is ignited by the high temperature generated through compression.

Diesel engines have higher compression ratios as compared to petrol engines because it is necessary to initiate combustion. The compression ratio indicates how much the gas inside the engine cylinders gets compressed.

For example, a compression ratio of 18:1 means that the volume of gas is reduced 18 times when the engine piston is at the top of its stroke.

The compression ratio is directly linked to engine efficiency. It is one of the reasons why diesel engines are more efficient than petrol engines.

On a final note about compression, forced induction (turbocharging and supercharging) increases the effective compression ratio. Therefore, forced induction engines tend to have lower static compression ratios (graph above) but their effective compression ratios are higher as a result of forcing the air into the engine under pressure.

Pretty much all modern diesel cars are turbocharged, so don’t let a low compression ratio (16:1) deceive you – their effective compression ratio can be pretty high. Also, diesel engines can operate at higher boost pressures than petrol engines because too much boost (or too high compression ratio) makes petrol engines susceptible to destructive knocking (detonation).

Lack of throttling losses

Another reason for better diesel efficiency is the lack of throttling losses. Petrol engines need to maintain a correct air-fuel ratio. Burning fuel inside an engine is a chemical reaction and the ingredients for optimal combustion are 14.7 grams of air and 1 gram of petrol.

The 14.7:1 ratio of air to fuel is the stoichiometric ratio. Petrol engines need to operate close to this value. Adding too much fuel means that the engine is running rich, which is inefficient because there isn’t enough air to completely burn all the fuel.

Too little fuel means that the engine is running lean. The problem with this is that a lean mixture is difficult to ignite, and it may increase combustion temperatures to dangerous levels, high enough to melt engine pistons in severe cases.

Even when the engine is capable of running lean, the emissions of nitrogen oxides (NO_x) can go through the roof. Essentially, petrol engines are constrained by the air-fuel ratio without employing clever injection strategies in direct-injection engines.

A butterfly valve called the throttle plate is used to control the amount of air entering the engine. It sits inside the throttle body attached to engine air intake. Here’s what it looks like:

The problem with the throttle plate is that it restricts airflow. At partial loads (partially depressed gas pedal), the throttle plate is only half open to reduce the amount of air entering the engine. This creates a vacuum in the intake manifold because the engine is trying to suck in more air than it is allowed to. Imagine trying to breathe through a straw.

The throttle plate reduces efficiency at partial engine loads and these losses are called throttling losses. There are some people out there who treat the gas pedal as an on-off switch. If you always drive a petrol car with the pedal to the metal, you are doing it right! At least as far as reducing throttling losses is concerned…

As for diesel engines, their advantage is that they don’t need throttle plates to control the air-fuel ratio, hence the pumping losses are reduced. Air-fuel ratios are not that important in diesel cars. They are happy to run on very lean mixtures, which is great for efficiency. Here’s how to control a diesel engine:

more fuel = more power

less fuel = less power

That’s pretty much it. You control the amount of fuel added by the fuel injectors and make sure there is enough air to burn it all. Too much air won’t hurt (to a certain point at which the engine blows up). Air-fuel ratios only become important, when you take engine emissions into account. I will get to this topic a bit later.

Fuel economy

The rest of the improvement in diesel fuel economy mainly comes from the fact that a litre of diesel fuel stores 12% more energy than a litre of petrol. In other words, this alone should give you 12% improved fuel economy in diesel cars because you can burn less fuel to perform the same amount of work.

If you take all of this into account, a modern diesel engine is about 20-25% more fuel efficient as compared to a direct injection petrol engine and closer to 30% more efficient when compared to a port-injected petrol engine. This is when comparing engines that are equivalent in terms of power output.

Longevity

There is one more advantage that diesel engines have that’s still valid today – it’s their longer lifespan. Diesel fuel, also called diesel oil, is a better lubricant than petrol, while petrol is a better solvent. Feeding a solvent into the combustion chamber works against the oil film that prevents pistons and cylinders from wearing.

Additionally, diesel engines are built stronger to withstand higher compression ratios, which also makes them more hard wearing. Because of this, the internal parts of a diesel engine tend to last longer.

In other words, diesel engines can do more miles before needing a rebuild or landing at the scrap yard. Please note that I’m referring to the engine internals. Unfortunately, I can’t say the same about the diesel injection system or the auxiliary parts that reduce emissions.

Some of these components have relatively short lifespans, which is the source of the high maintenance cost of diesel engines. I will explain in a moment.

Diesel engine emissions

The combustion in diesel engines occurs as soon as fuel is injected. Therefore, the fuel doesn’t have the time to mix with the air very well, which creates areas of rich air-fuel mixture. As a result, these areas of high fuel concentration don’t burn cleanly. They are the source of particulate matter (soot) that diesel engines are infamous for.

This is also the reason why manufacturers keep increasing the fuel injection pressures to ridiculous levels in order to make the fuel mix better with the air. Apart from soot, diesel engines emit high levels of nitrogen oxides (NO_x) due to the lean-burning nature of diesel combustion.

Pick your poison – particulate matter will give you cancer and nitrogen dioxide is a great asthma trigger. Also, nitrogen oxides are linked to acid rain, while soot is linked to smog. This is why diesel cars are getting banned from entering city centres around the world. The black smoke that you sometimes see behind diesel cars is the particulate matter (soot).

On a positive note, diesel engines are pretty good when it comes to carbon dioxide (CO2) emissions. The amount of CO2 emitted by a combustion engine is linked to its efficiency. Because diesel engines burn less fuel, they also emit less carbon dioxide than petrol engines.

Emission standards

Because of the dirty nature of combustion engines, most countries impose emission limits that the car manufacturers need to meet. These emission standards became so stringent that getting diesel engines to pass has become very difficult and requires many engineering workarounds.

While emissions from petrol engines can be dramatically reduced by catalytic converters, diesel engines require a lot more exhaust after-treatment.

For diesel engines to conform to the Euro 6 emission standards that came into force in 2015, all diesel cars need to be fitted with Diesel Particulate Filters (DPF) and many cars will require Selective Catalytic Reduction (SCR) systems that spray ammonia or urea into an SCR catalytic converter mounted to the exhaust system.

Countries outside of Europe, the United States, Australia, China and Japan follow a similar pattern of regulations with similar limits imposed.

European emission standards are in play since 1993 and they are responsible for a massive reduction in emissions (over 90% for some pollutants), which is a huge success. However, success comes at a price in this case.

The first major change that Euro emission standards introduced was mandating the use of catalytic converters in petrol cars since 1993. As for diesel engines, emission limits started becoming problematic for drivers and manufacturers with the introduction of Euro 4.

• Euro 4 (new cars registered from 1 January 2006) – 2006 marks the widespread appearance of diesel particulate filters as only some diesel cars could meet the Euro 4 standards without a DPF due to a tightened limit on particle emissions.

• Euro 5 (new cars registered from 1 January 2011) – the use of diesel particulate filters became mandatory. Also, a tightened NO_x emissions limit meant that some cars had to be fitted with NO_x traps, which proved to be not as effective as expected (VW emissions scandal). Also, some cars were already fitted with SCR systems, which were used as an alternative to NO_x traps.

• Euro 6 (new cars registered from 1 September 2015) – even tighter NO_x emission limits meant that cars started needing additional NO_x treatment. Euro 6 marks the widespread appearance of SCR systems. Time will tell how reliable the SCR systems are and how long they will last.

Common problems with diesel engines

Okay, enough about the boring emission standards. It’s time to get to the point of this article.

Car manufacturers have finally managed to make diesel engines nearly as clean, quiet and refined as petrol engines. As is often the case, this comes at a price because engineering design at this level of technological maturity is almost always a compromise. The price to pay is the high maintenance cost of modern diesel cars once they reach a certain mileage.

While the internal parts of a modern diesel engine are still more long-lasting as compared with petrol engines, the injection system and the emissions control equipment is fragile.

Some of these components may need to be serviced multiple times before the engine itself is worn-out. This is the source of the higher maintenance cost of diesel engines, especially high-mileage engines.

Below is a list of things that often fail in diesel cars.

Diesel Particulate Filter (DPF)

Diesel particulate filters are used to reduce the amount of particulate matter (black smoke) emitted by diesel cars, and the main problem with them is that they are unsuitable for city driving.

You can think of the DPF as soot trap. The soot remains trapped in the filter while the exhaust gases get released into the atmosphere. The soot storage capacity is limited. The particulate matter needs to be burned off before the DPF becomes full. Burning off the particulate matter creates extra CO2 and some ash.

Here’s what a DPF looks like inside:

Burning off the soot is called regeneration. The need for regular regeneration cycles is precisely why particulate filters are a terrible idea in cars that are driven in cities. There are three types of DPF regeneration cycles:

Passive regeneration

This type of regeneration happens when the exhaust temperature is high enough, i.e. during motorway driving. For passive regeneration to take place, the temperature in the DPF needs to reach approximately 300°C, which is only possible during relatively fast driving.

Passive regeneration is a slow oxidation process and it may not be enough to fully clear the soot, and not all cars are capable of passively regenerating anyway.

There are very few people that use their cars only on the motorway. Short trips or start-stop driving does not allow the exhaust temperature to get high enough to initiate passive regeneration. Therefore, car manufacturers implemented a solution to force the exhaust temperature to rise to around 600ºC and clear out the DPF. It is called active regeneration.

Active regeneration

When the car detects that the diesel particle filter is becoming clogged (around 50% full) it will try to initiate an active regeneration cycle. Active regeneration is typically required every 300-700 miles in typical driving (urban + motorway). Increasing the exhaust temperature is done by injecting extra fuel into the exhaust, where it burns.

In a way, actively regenerating the DPF is like bombing for peace (or f***ing for virginity). Cars fitted with diesel particulate filters burn more fuel than cars without. The total pollution is higher.

Nevertheless, particulate filters are actually quite effective, and cars with DPFs emit even 90% less particulate matter. The extra CO2 emitted by cars with particulate filters is the lesser evil when compared to the particulate matter that gets burned away.

Active regeneration usually takes 5-15 minutes of continuous driving, ideally at a constant speed. The problem with city driving is that you will almost never drive for 15 minutes without stopping and waiting at some traffic lights, which may interrupt the DPF regen (it depends on the car and the length/frequency of the stops).

In fact, the car is unlikely to even enter the regeneration cycle during urban stop-and-go driving. Also, turning the engine off during a regeneration cycle is a bad thing. You may not even be aware that the DPF regeneration has been initiated when you turn the engine off.

Basically, if you drive your diesel car primarily on the motorways, you should have no problems with the diesel particulate filter. However, if you drive a car with a DPF mostly in the city, well, you bought the wrong car.

Forced regeneration

If the active regeneration cycle gets interrupted too many times or it never has a chance to even start, the DPF will continue to accumulate particulate matter.

At some point, it will be so clogged that it will put the car into “Limp Home” mode and illuminate the “Check Engine” light. At this point, the car needs to be taken to a specialist to perform a forced regeneration (also called service regeneration).

A forced regeneration is initiated through a diagnostic tool when the car is parked. The idle RPM rises and the engine dumps fuel into the exhaust to burn off the soot – all in the name of ecology!

Here’s what forced regeneration looks like:

It’s worth mentioning that there is a variant of the diesel particulate filter that uses an additive, called Eolys fluid, which can lower the temperature required to burn off the particulate matter.

This variant of the DPF is used by the French PSA Group (car brands: Peugeot, Citroën and Vauxhall/Opel since 2017). It is called “Filtre à Particules” in French or simply FAP.

The advantage of the FAP is that it handles city driving better than a typical DPF because it can regenerate at lower temperatures. Its disadvantage is the need for additive refills every 80,000 miles or so, and the system is even more complex.

DPF Lifespan

The typical lifespan of a diesel particulate filter is somewhere between 150,000 and 200,000 miles when the car is used and maintained correctly. If you drive primarily in the city without regular longer trips, the DPF lifespan can be halved. Buying a diesel car with a DPF for urban driving is a false economy.

The DPF itself is fairly reliable. It’s just that it is sensitive to poor maintenance and abuse. Cars with diesel particulate filters require low ash engine oil and regular regeneration cycles. Also, the engine needs to be in good working order. Problems with the EGR valve, injectors or driving with a faulty thermostat will reduce the DPF lifespan.

Buying a high-mileage diesel car, even when maintained properly, can be a bit of a gamble. However, not knowing the car’s history increases the risk substantially. The DPF may be on its last leg after doing supermarket visits for the last 20,000 miles and running on some cheap engine oil that’s not suitable for diesel particulate filters.

When the time to replace the DPF comes, it will typically cost between £500 and £1500. Although, I’m sure you could double this figure if you take a premium class car to the dealership for a DPF replacement. Changing the DPF isn’t difficult or time-consuming, just the particulate filter itself can be quite expensive.

Removing the DPF permanently is possible (it’s called a DPF delete). However, it is also illegal in the UK and probably in most other countries. If the DPF is removed, the car’s ECU needs to be reprogrammed to stop dumping fuel into the exhaust system.

EGR Valve

All modern petrol and diesel cars are fitted with an Exhaust Gas Recirculation (EGR) system. The key part of the system is the EGR valve. Its function is to feed the exhaust gases back into the engine to reduce emissions of nitrogen oxides. This happens only during low and medium engine loads. At full throttle, the EGR valve closes and no exhaust fumes are returned to the engine.

The EGR system in petrol cars is usually reliable because the exhaust gases contain a fraction of the particulate matter as compared to diesel engines. Also, the amount of exhaust fumes that gets recirculated is a lot smaller.

Apart from reducing emissions in petrol cars, the EGR reduces throttling losses, which improves efficiency. It also makes the engine reach operating temperature quicker (hot exhaust fumes returning to the engine). The EGR in petrol cars is a good thing.

It’s a different story in diesel cars. You don’t get the benefit of reducing throttling losses, and the EGR valve leads a much more difficult and shorter life. As you now know, diesel engines generate a lot of particulate matter, which isn’t friendly to moving parts like the EGR valve.

A common problem in diesel engines is the EGR valve getting stuck because of carbon deposits. You would be surprised how much sludge and carbon gets deposited in the air intake manifold due to EGR action.

At 100,000 miles the EGR valve is likely to be full of carbon and ripe for replacement. If there is reasonable access to the EGR valve in your car, I recommend taking it out and cleaning out the soot every 50,000 miles. This should prolong the EGR valve life expectancy noticeably.

Keep in mind that 100,000 miles is a very rough estimate. In some cars, the EGR valves are a recurring problem due to poor design and may need replacing every 50,000 miles. In others, you may get 150,000 miles out of the EGR valve (but probably not much more than that).

Replacing the EGR valve costs somewhere between £300 and £600 at an independent repair shop. The price depends on the location of the valve – some are quite difficult to get to.

Just like with the DPF, short journeys mean more carbon build-up and shorter EGR valve lifespan. The EGR system recirculates exhaust fumes during idle, low loads and low RPM. When you step on the gas, the EGR valve should close, as long as it’s not stuck.

An EGR valve that doesn’t fully close will reduce power and increase fuel consumption. To add insult to injury, a problem with the EGR may cause issues with the diesel particulate filter.

Swirl Flaps

Swirl flaps live in the air intake manifold. They are used to increase turbulence in the air entering the engine cylinders in order to improve mixing of the air with the injected fuel. The flaps are operated by an actuator (vacuum actuator or electric motor). They close at idle and low engine speeds to create a swirl in the air going into the cylinders.

At high engine speeds and high loads, the swirl flaps open to increase the airflow. The whole point of swirl flaps is to reduce emissions. They may also slightly improve engine torque at low revs. High RPM torque and power output are not affected unless the swirl flaps don’t work properly or carbon build-up becomes severe. In these cases, they become a restriction.

Swirl flaps are mechanical parts. I’m sure you can already guess what happens to moving parts that are subjected to diesel exhaust fumes. Swirl flap failure is a common problem in diesel engines and the main cause is the EGR valve.

The flaps fail because of increased friction in the mechanism caused by carbon build-up. Carbon build-up is a side-effect of feeding exhaust gases back into the engine (EGR valve). Swirl flaps are also used in petrol cars. However, when they are designed well, they aren’t as problematic.

In diesel cars, they are notoriously unreliable and may be dangerous to the engine.

Swirl flap failure

The swirl flaps can fail in a few ways:

• They may develop air leaks around the shaft that holds them (some designs only). The result is a loss of boost pressure and reduced engine performance, eventually followed by the “Check Engine” light.

• The mechanism that adjusts the swirl flaps may fail. Depending on the manufacturer, you may see broken levers, fried servomotors or leaking vacuum actuators.

• A swirl flap may become detached and get ingested by the engine. This is the worst-case scenario. An ingested flap can damage valves, cylinder walls, the piston, the fuel injector, and even the turbocharger. Unfortunately, some engines are known for swallowing swirl flaps. The extent of damage depends on plain luck and whether the swirl flap is made of metal or plastic.

Essentially, the EGR and swirl flaps are two systems that don’t work well together. Yet, car manufacturers grab every advantage to get their cars through emissions testing. In this case, it’s at the cost of reliability (and some wrecked engines). In my opinion, swirl flaps should not be used in diesel engines.

I’m dead serious about swirl flaps being dangerous to the engine. I recommend doing some research before buying a modern diesel car because there are cars out there with some really poor swirl flap designs. Have a look in the car directory on this site. You may find some information about dodgy swirl flaps in particular car models.

If the car model you are looking to buy is fitted with “high risk” swirl flaps, you should take some precautions, like replacing the intake manifold with a new one. A brand new manifold should be safe for quite a while.

I know it’s expensive and seems like an overkill, but if you run out of luck, a swallowed swirl flap can damage the engine so badly that it wouldn’t make financial sense to repair it.

An alternative option is to remove the swirl flaps altogether. Swirl flap removal kits are inexpensive and widely available. Keep in mind that this option is illegal because it increases emissions. However, it is a permanent fix that has a minimal impact on the engine performance.

Dual-mass Flywheel (DMF)

A dual-mass flywheel failure is definitely one of my favourite first-world problems. The dual-mass flywheel is a torsional damper fitted between the engine and the clutch. Its job is to smooth out the jerky nature of the engine’s power delivery.

When engine cylinders fire, there is a surge of rapid crankshaft acceleration, then a pause, then another surge from the next cylinder firing and so on. In other words, the engine delivers power in pulses, rather than constantly. The purpose of the dual-mass flywheel is to reduce noise and vibrations in the cabin. It also protects the drivetrain from torsional vibrations.

If the torsional vibrations are not dampened, they can manifest as transmission gear rattle at standstill or vibrations/noise when driving at low engine speeds (below 2000 RPM). Dual-mass flywheels make cars smoother and quieter. If this sounds great, wait until you get the bill for replacing the DMF in your car.

Dual-mass flywheel replacement typically costs between £700 and £1200. This includes the cost of a new clutch since it’s worth doing it at the same time to avoid paying for the same work in the future. It’s a labour intensive job because the gearbox needs to be removed from the car.

The price above is what independent car repair shop will charge you. If you take the car to the dealership, you can add 50% or double those figures.

The main problem with dual-mass flywheels is that the improvement in comfort and noise is often so small that it doesn’t justify the cost of the DMF and the reduction in reliability as compared to using a single-mass (solid) flywheel.

A traditional single-mass flywheel is a solid piece of metal that relies on its inertia to smooth out engine’s power delivery. Solid flywheels are inexpensive and don’t really wear out when not abused. A single-mass flywheel should last the lifetime of the vehicle.

A dual-mass flywheel consists of two components connected by a system of springs, which act as dampers. In a diesel car, you can treat the dual-mass flywheel as a consumable item.

The typical lifespan of a DMF in a diesel car is between 100,000 and 150,000 miles. Although, I reckon that you could finish the OEM dual-mass flywheel off in 50,000 miles in some cars with 100% urban driving at low engine revs.

Dual-mass flywheels fail much quicker in diesel cars as compared to petrol cars because they get pummeled by the higher level of torsional vibrations.

Driving at low engine speeds (1000-1500 RPM) shortens the lifespan of the dual-mass flywheel. I find it funny that the DMF makes it possible to drive at such low revs comfortably, but it’s exactly what makes it wear out quicker.

Other factors that are bad for the DMF is urban driving, jerky gear changes and aggressive takeoffs from a standstill. The dual-mass flywheel is yet another reason to avoid buying a diesel car for driving in the city.

Solid flywheel conversion

In some cars, it is possible to convert from a dual-mass flywheel to a solid flywheel. It’s cheaper and some people choose to do so to avoid recurring problems (popular decision among fleet owners). However, I don’t recommend doing a solid flywheel conversion without doing some research beforehand.

The extra vibrations may damage the transmission in some cars because the gearbox may not have been designed to work with a solid flywheel to begin with. On the other hand, some cars run perfectly fine with solid flywheels with a minimal difference in the level of noise and vibrations.

Please note that solid flywheels also dampen torsional vibrations. It’s just that dual-mass flywheels do it better. The springs in the clutch plate (see picture below) act as dampers in cars with single mass flywheels. Cars with dual-mass flywheels may or may not have these springs. The ones that don’t have springs, rely solely on the DMF for damping.

Diesel fuel injectors (Common Rail)

Improvements in fuel injection technology are what made modern diesel cars less diesely (for a lack of a better word). The injection technology used today is called Common Rail from the “common” high-pressure fuel rail that feeds the injectors.

The diesel fuel injectors are the key parts that define the performance of a diesel engine as they directly affect the combustion efficiency and emissions. As the name implies, their role is to inject diesel fuel into the engine cylinders at high pressures. When I say high, I mean ludicrously high when it comes to the latest Common Rail diesel engines.

Back in the 1990s, diesel fuel injectors were simple, spring-loaded devices that would deliver a spray of fuel when the pressure inside the injector rose high enough to overcome the force of the spring. The injection pressure in the old-school diesel engines with indirect injection was lower than 150 bar (150 times the atmospheric pressure). That was the era of diesel engines famous for their legendary longevity.

Soon after, direct injection technology was developed. The improvement in fuel economy, power and refinement made direct injection turbo-diesel cars more popular. From that moment on, car manufacturers have been increasing injection pressures and reducing the diameters of the orifices in the fuel injector tips.

Modern, Common Rail injectors can deliver fuel at 2500 bar, which is 20 times more than what was typical for diesel cars of the 1990s. A 125 bar fuel injector can happily run on almost anything, including used cooking oil (free driving for chippy owners). A 2500 bar fuel injector will throw a hissing fit very quickly when fed anything else than good quality, perfectly clean diesel fuel.

By squeezing fuel at higher pressures through a smaller hole (orifice), the fuel spray coming out from the injector consists of smaller droplets (better fuel atomization).

Well atomized fuel mixes better with the air. Also, many small droplets have a larger combined surface area than fewer large droplets (more efficient burn). This leads to a more complete combustion, more power, better efficiency and less smoke.

The other major improvement in diesel injector technology is the ability of piezoelectric and solenoid injectors to deliver multiple injections per combustion cycle. The state-of-the-art piezoelectric injectors can deliver up to nine injections in one cycle and dose fuel in milligrams.

The typical diesel knock and emissions are reduced by spreading the injections into stages (pilot injections, main injections, post-injections). Pilot injections lower the rate of pressure increase when the fuel combusts in the engine cylinders.

In other words, the combustion moves closer to “burning” and further away from “exploding”, which makes the engine sound smoother and quieter. That’s why some modern diesel cars are not much louder than petrol cars.

So what’s the catch?

Improvements in injection technology are what made diesel cars what they are today – quiet, powerful and efficient. However, such improvement is bound to come at a cost at this level of technological maturity. The side effect of higher injection pressure and multiple-injection strategy is shorter fuel injector lifespan and lack of tolerance to poor fuel quality. Additionally, the injector cost is exponentially higher.

The higher the injection pressure, the higher the abrasive action of fuel being forced through 0.1 mm holes (orifices). Have you heard of waterjet cutting? It is a technique of cutting through stuff, including metal and stone. It uses water at high pressure mixed with abrasive particles. Do you notice any similarities?

Also, diesel fuel injectors have a finite design life. Let’s say that the fuel injector can only fire 1000000000 times (I made this number up). By following this logic:

Will an injector that fires 8 times per combustion cycle have a 4 times shorter lifespan than an injector that fires 2 times per cycle?

Food for thought – let me know what you think in the comments section!

I’m not trying to scare you though. Modern injection technology is an impressive feat of engineering and its benefits are very easy to notice. Nevertheless, diesel fuel injectors are precision devices, and they are not nearly as simple as they used to be.

New fuel injectors typically cost between £200 and £300 per piece. You may need a new set somewhere between 150,000 and 200,000 miles.

There is also the option of injector reconditioning for about half the price of a new set. However, keep in mind that not all modern piezoelectric injectors can be reconditioned. Also, reconditioned fuel injectors won’t last as long as new ones.

Buying a used diesel car

Modern diesel cars are great when they are new. However, problems often start when the car approaches the 150,000 miles mark. For the sake of example, let’s say that you bought one with 150,000 miles on the clock, and you are planning to keep it for three or four years.

The car still has the original dual-mass flywheel, injectors and even the EGR valve managed to survive this long. The original diesel particulate filter is there too, but if you’re not interested in cars, you probably didn’t even know about it (you will after reading this article!).

Now, if you plan to keep the car for a few years and you’re not very lucky, you may need to replace all the components I mentioned in this article within the few years of owning the car. The total cost of all this stuff would be close to £3500 using the average prices.

It still does not include any swirl flap maintenance. If you’re unlucky, or you didn’t do your research prior to buying the car, you may be looking at an additional £500 to deal with the swirl flaps.

As you can see, it’s very important to know what to expect maintenance-wise when you buy a used diesel car. High mileage diesel cars are nearly as expensive to maintain as the Space Shuttle. Joking aside, if you buy a modern diesel car in poor condition or you’re simply unlucky, you may have to pay through the nose to keep the car going.

This is why second-hand, modern diesel cars only make sense for people who drive a lot. My back-of-a-cigarette-packet calculations tell me that you should be doing at least 12,000 miles every year for the fuel savings to offset the potential cost of maintenance.

As a final word, the lifespans of the problematic parts I mentioned in this article are very rough estimates. They are not set in stone. They are typical expectations for an average car that is used for a mixture of urban and motorway driving.

If you look after your diesel car well, and 80% of your driving is on the motorway, there’s no reason why a DPF or other components should not last 200,000 miles. Urban driving is usually the problem.

Summary

Here’s a quick summary of what you should take away from all this:

• Modern diesel exhaust system is a sophisticated chemical reactor. It’s no longer just a piece of pipe with a muffler. Exhaust gases get recirculated back to the engine. The catalytic converter turns the hydrocarbons and CO into CO2 and water. The diesel particulate filter traps soot and burns it off when it gets full. Then there is the NO_x removal system. Some of the components in these systems are not very reliable. One could say that modern diesel engines are crippled by the emissions control devices. It’s a shame that smog isn’t healthy.

• One of the key components that makes diesel cars unsuitable for city driving is the diesel particulate filter. If you rarely leave the city for a longer trip, you are likely to dramatically reduce the lifespan of the DPF in your diesel car. With diesel cars getting banned from entering city centres all over the world because of their emissions, I feel that diesel engines don’t make much sense in passenger vehicles unless you drive a lot – enough for the fuel savings to offset the high maintenance cost and then some.

• The improvements in fuel injection technology and the use of dual-mass flywheels managed to turn a frog into a prince. Today’s diesel cars may be powerful, quiet and very nice to drive, but the complexity has gone through the roof. Along with the complexity, so did the maintenance burden. Progress is vital, but there is a point where the next small bit of extra performance comes at the cost of a larger chunk of reliability. When progress compromises reliability, I think it’s time to stop. I feel that modern diesel cars have gone past this point.

Older was better?

In the past, diesel engines could operate without electricity once started. Everything was purely mechanical and such engines were still used in passenger cars in the 1990s.

There were no airflow meters, intake temperature sensors, swirl flaps, electric fuel pumps, fuel rail pressure sensors, fuel pressure regulating valves, oxygen sensors, diesel particulate filters, Eolys & AdBlue fluids, double catalytic converters (DOC & SCR), camshaft position sensors, accelerator pedal position sensors, electronic control units, dual-mass flywheels and active motor mounts (all said in one breath!).

Even without all these things, the last of the indirectly injected diesel engines were already reasonably powerful and well-mannered while still being very reliable. All that was required to get them to run was a mechanical injection pump, spring-loaded fuel injectors and some optional electronic bits. Pilot injections were possible too (by using two springs)!

The first-generation directly injected diesel engines were quite good too, albeit a lot more complex and more expensive to maintain. Then, the emission limits started becoming tighter. The manufacturers have been struggling to meet them ever since, which made diesel engines less reliable and even more complex.

Today, we’ve got fuel injection systems that run at pressures high enough to cut through things. Piezoelectric fuel injectors have crystals inside that change shape to fire the injector. Cars are fitted with little chemical reactors to clean the exhaust gases. Everything is governed by computers more powerful than what was necessary to put people on the moon.

The original simplicity of diesel engines has been lost. Welcome to the space age.

If you liked this article, please share it with your friends!

And here’s more on the topic of progress.

The post The Problem with Modern Diesel Engines appeared first on Still Running Strong.

Do you know what a timing belt or a timing chain is? And more importantly, do you know what happens if it fails? If you don’t, this is an article for you! You are going to learn something vital to maintaining your car.

If none of this sounds new, you can skip to the second half of this article for some practical information, like how to quickly check if a timing chain is still good.

Engine timing – valves & pistons

A typical car engine is based on the reciprocating motion of pistons inside cylinders. The combustion of air and fuel in the cylinders pushes the pistons down, which then drive the crankshaft. You can think of the crankshaft as the main shaft of the engine that all the pistons are connected to.

There is another very important shaft – the camshaft (at least one in each engine). The camshaft has a series of cam lobes that push on the engine valves to open them at the right times. The valves control the flow of fresh air into the cylinders and the flow of exhaust gases out. For the engine to function properly, the movement of the valves and pistons must be synchronized.

Interference & non-interference engines

The piston and valve synchronization is not only important for the operation of the engine but also its integrity. If the valve timing goes out of sync, the pistons may hit the valves. This is because, at certain times during the engine operation, they all occupy the same space.

Engines that are designed in such a way are called interference engines because the valves and pistons can interfere with each other. You can replace the word “interfere” with “smash” if you like.

The interference engine design is a byproduct or high compression ratios in modern engines and the use of more than two valves per cylinder, which requires the combustion chamber to have a certain shape. The majority of modern engines are interference designs.

By contrast, a non-interference engine will simply freewheel to a stop when the timing belt or chain breaks. That’s because the clearance between the valves and pistons is large enough that they cannot collide.

A good example of a non-interference engine is the Fiat’s 8-valve “FIRE” used in all the generations of the Fiat Panda since 1986. The little FIRE engine remained a non-interference design until 2010 when variable valve timing was added and compression increased to meet Euro 5 emission standards.

Have a look at the video below. Pay attention to how closely the pistons and valves work to each other in an interference engine.

Okay, let’s get to the point. To maintain the correct timing between the valves and the pistons, the crankshaft and the camshaft(s) must rotate in sync. The camshaft is driven off the crankshaft. In the vast majority of modern car engines, this is achieved by using a timing belt or a timing chain.

Sometimes, gears are used too, but that’s quite rare. The timing belts and chains are the two most common solutions so we’ll focus on them.

Timing chains

I’m sure you remember what a bicycle chain looks like. It’s called a roller chain and it’s one of the two types of timing chains commonly used in car engines. The other type is called a silent chain, just like the one in the video above.

Regardless of the chain type, one of the two main differences between a timing chain and a timing belt is that the chain lives inside the engine, where it is lubricated by engine oil. On the contrary, a timing belt runs dry. The timing belt is usually hidden under a plastic cover.

The other major difference is the lifespan. A well-designed timing chain should last the “lifetime” of the engine, while a timing belt will typically need replacing every 60,000 – 100,000 miles. We’ll get back to the definition of “lifetime” later.

Apart from the chain, the other key components that support the timing chain are the chain guides and the chain tensioner. The chain guides lead the chain through the engine and prevent it from slapping against the chain casing, while the chain tensioner applies tension to the chain to prevent it from skipping teeth.

The tensioner uses the pressure of the engine oil to do this. That’s why it’s called a hydraulic tensioner.

Here’s what it all looks like:

Timing belts

The timing belt, also called the cambelt, is a toothed belt that works together with matching toothed pulleys. Because of the teeth, it cannot slip. Therefore, it can be used to maintain the timing between the crankshaft and the camshaft(s).

The timing belt must be kept in constant tension by the timing belt tensioner. This is to prevent it from jumping teeth on the pulleys, which would mess up the engine timing. In a typical car engine, there is also one or two idler pulleys that guide the timing belt.

In the majority of cars with a timing belt, the water pump is also driven by the timing belt. The water pump is not an essential part of the timing system. Therefore, in some engines, it is driven by the auxiliary belt.

Here’s what a typical timing belt setup looks like in a 4-cylinder engine with the water pump driven by the cambelt:

When worlds collide

So what really happens when the valve timing goes out of sync in an interference engine?

The best case scenario is an engine that runs poorly or doesn’t run at all if the cambelt/chain just skipped a tooth. The worst case scenario is a badly damaged engine if too many teeth are skipped or the cambelt/chain breaks. The damage is caused by the valves colliding with the pistons.

If you’re lucky, you may get away with some bent valves and no other damage. New valves are not expensive but the amount of work required to fit them is quite extensive. The air intake, the injection system, the exhaust manifold, the timing cambelt/chain, and the cylinder head – all these components need to be removed to get to the valves.

If you’re not so lucky, a valve may punch a hole in a piston and even the crankshaft bearings may get damaged. Either way, fixing an engine wrecked by a failed timing belt or chain is either expensive or very expensive.

Timing belt maintenance

All cars fitted with a timing belt have a specified belt replacement interval. You will find it in the car owner’s manual. The service intervals vary, but typically it’s between 50,000 and 100,000 miles. The cambelt is made of rubber so it degrades over time. Even if you don’t drive much, you will still need to replace it every 5 – 10 years.

Whenever the timing belt is due for renewal, it should be replaced along with the tensioner, idler pulleys and the water pump. All components are equally important.

For example, a water pump with worn out bearings can seize and snap the timing belt. It’s not worth trying to save £25 by not replacing a pulley or the water pump. A water pump that fails can take out the timing belt and crash your engine.

If you are going to spend time or money disassembling everything in the way to the cambelt, you should do the job properly and renew all the components. When you pay someone to do it, please make sure all the parts are replaced, not just the belt.

If you are going to buy a used car with a timing belt, find out if the previous owner replaced the timing belt as specified in the service manual. If it’s not due yet, it will likely be up to you to get it done in the future.

However, it’s a bad sign if the cambelt replacement is overdue or the seller doesn’t know whether it was replaced or not. What else has been neglected?. If you don’t know when the cambelt was last replaced, replacing it should be the first thing to do if you decide to buy such a car.

Timing belt replacement cost

The usual cost of a timing belt replacement, along with the tensioner, pulleys and the water pump is £300 – £500 in an independent car repair shop. This is a typical timing belt replacement cost for a 4-cylinder engine.

If it’s a V6 or a V8, it usually costs more. You may have to pay £400 – £800 for a timing belt replacement in these larger engines. This is because there are more parts to replace and it’s often more difficult to access the timing belt because of the larger engine.

Keep in mind that these are independent garage prices. Dealerships can charge even up to 50% more. However, sometimes you can get a good deal if you have a car with a popular engine.

I recommend contacting your local dealership to make sure the interval specified in your car owner’s manual is still valid. Sometimes, the service recommendations change. There have been instances where a car manufacturer cut the replacement interval in half because of an over-optimistic initial recommendation.

Symptoms of a bad timing belt

Unfortunately, a bad timing belt rarely shows any symptoms of a problem until it’s too late. If the belt skips a tooth, you would notice it because the engine would run poorly or not run at all.

Obviously, you don’t ever want the timing belt to reach a point where it skips teeth or breaks, as it can seriously damage the engine.

There may be no obvious symptoms before timing belt failure, however, there are a few warning signs to look out for:

• clicking noises coming from the timing belt cover

• squeaking or whirring noises – this may be a bad bearing in the water pump or one of the pulleys

• oil coming from the timing belt cover – this may be a leaking camshaft seal. Oil will ruin the timing belt, so it’s important to fix this quickly (and replace the timing belt).

If you’re worried, you can visually inspect the timing belt. Removing the timing belt cover (or at least a part of it) is usually not that difficult.

Timing chain maintenance

Generally, when a timing chain is used, the intention is for it to last the “lifetime” of the engine. “Lifetime” can be very roughly defined as 200,000 miles.

Timing chains are meant to be a lot more durable than timing belts, and for this reason, the manufacturers don’t usually specify a replacement interval (please check your car owner’s manual).

Typically, you are only meant to replace the timing chain or other chain drive components when there is a problem. Most problems are usually related to a loose chain. It’s common to say that a chain has “stretched“.

A stretched chain is at risk of skipping teeth and altering the timing of the engine (with bad or catastrophic consequences). Typically, loose timing chains become noisy when they flop around inside the casing.

Just for clarification, chains don’t really stretch – it’s the wear on the pins that makes the chain longer. Additionally, as the timing gears wear, their diameter is reduced, which adds to the slack in the system. Also, the tensioner may be failing to apply enough tension to the chain.

You are probably wondering if chains can really last for 200,000 miles.

It depends.

There have been cases of cars that routinely managed to do a lot more than 200,000 miles on their original timing chains. Everything comes down to correct maintenance and the design of the engine:

• The timing chain in an inline engine should last longer than in a V-type engine simply because it is shorter. Therefore, it’s less susceptible to stretching (cumulative wear of the chain pins). Also, the fewer gears a chain has to go over, the longer it will last (less movement of the pins and less wear on the rollers).

• Insufficient lubrication can shorten the chain lifespan dramatically. That’s why it’s important to use good quality engine oil and replace it regularly.

• A double row roller chain is more durable than a single row roller chain.

• The weakest component defines the life of the system. What I’m trying to say is that apart from the chain, the chain tensioner, sprockets and chain guides must last long enough. Often, it’s the chain tensioner that gives up first. Also, there have been many cases of plastic chain guides failing before the chain or the tensioner.

Some of the 1980s Mercedes-Benz engines are great examples when it comes to long-lasting timing chains. Some of these cars managed to do over 300,000 miles on their original chains and that was using inferior engine oils when compared to what is available today.

Don’t try this at home though. When you get near 200,000 miles, you should consider replacing the timing chain, chain tensioner and chain guides in any car. They are moving parts, and they will eventually wear out even in the most robust engines.

On the other end of the spectrum, there are engines that typically fall short of reaching our definition of “lifetime”. This is usually caused by some kind of design flaw, for example, insufficient oil supply to the timing chain, weak plastic chain guides or simply an undersized timing chain. Keep in mind that poor maintenance will also reduce the lifespan of the system.

I recommend doing some research before buying a used car with a timing chain because your peace of mind may be interrupted by the timing chain rattle of doom the first time you start your newly-acquired car in the morning. There is a basic check you can do before buying a car with a timing chain – more will be explained below.

Timing chain replacement cost

Timing chain replacement is more expensive than renewing a timing belt. The parts are more expensive and it’s more difficult to access the timing chain.

Timing chain replacement typically costs £400 – £2000 in an independent garage.

Simple 4-cylinder engines with a single timing chain fall in the lower end of the spectrum. V6 and V8 engines with more than one timing chain fall in the upper end of the spectrum.

As you can see, the price range is quite wide. That’s because some larger engines may have even four timing chains (and four tensioners). Additionally, some cars have the timing chain at the back of the engine. This is because some manufacturers assume that the chain will not need replacing (nonsense!).

The price range can be even wider when you take the car to a dealership for timing chain replacement. Dealership prices fall in the range of £500 – £4000.

Having to replace a timing chain may not be that big of a deal if you are planning to keep the car for a few years (depending on the cost!). It’ll give you peace of mind for a long time.

However, a manufacturer of an engine with a timing chain system that wears out before reaching 100,000 miles deserves the middle finger, in my humble opinion. That’s because timing chains can last twice as long when the design is not compromised by cost-cutting or design flaws.

I can’t see the point of making a car with a metal timing chain that lasts shorter than a rubber timing belt…

Okay, enough ranting. Let’s get back on track.

Symptoms of a bad timing chain

Usually, the first symptom of a timing chain problem is chain noise (rattle) for the first couple seconds after a cold start. If you are planning to buy a car with a timing chain (or you already own one), you should establish the condition of the timing system.

A simple test you can do is to listen for any chain noise when the engine is started. This needs to be a cold start after the car has stood still for a couple hours (ideally overnight). It’s because you want to listen to the engine when the oil hasn’t reached the chain tensioner yet.

After a long standstill, the oil drains to the sump and it takes a couple seconds for the oil pump to distribute it all over the engine.

A loose chain will make a rattling noise before the tensioner takes out the slack. The more slack in the system, the longer the noise will last and the louder it will be. If the timing chain noise is persistent, it means the chain drive is on its last leg.

Open the bonnet, stand near the engine and ask someone to start the car for you. If you can hear a rattle that disappears after a couple seconds, it’s most likely a chain that has stretched too much or a failing chain tensioner. It’s a typical symptom of a loose chain. I recommend that you don’t buy such a car unless you are planning to service the timing chain as part of preventative maintenance.

There are two types of tensioners used in car engines – a ratcheting and a non-ratcheting design. The ratcheting tensioner has a mechanism that prevents the tensioner from withdrawing when there is no engine oil pressure, for example, during the first couple seconds after the engine is started. The non-ratcheting tensioner doesn’t have this mechanism and relies on a spring to maintain some chain tension before oil pressure builds up.

In my opinion, it is acceptable for an engine with a non-ratcheting tensioner to have a mild rattle for around a second after a cold start. As for an engine with a ratcheting tensioner, try to find a car that doesn’t rattle at all.

Treat this as a guideline, not a stiff rule. There is no standard for how long the timing chain noise should last and the best thing to do is to compare cars with the same engine models to see if one sounds better than the other. Ideally, when the timing chain system is in good condition (and not poorly designed), there should be no noise at all, regardless of the tensioner design.

Marbles in a can (timing chain noise)

Here’s a collection of videos showing what timing chain noise sounds like:

• Rattly Fiat 1.3 Multijet – If your car sounds like this, I recommend getting it serviced immediately. The chain rattle is very noticeable even though it’s a loud diesel engine.

• Less rattly Fiat 1.3 Multijet – Same engine as above but less noisy. Still, a rattle like this is not a good sign and likely qualifies for a service visit.

• Very rattly Volkswagen 1.6 FSI – This is exactly what you don’t want to hear. This could be a loose timing chain or a worn-out cam adjuster (cars with VVT only). The noise is a bad sign regardless.

• Too rattly Volkswagen 2.0 TSI – The noise lasts only for about 2 seconds but that’s not good enough because this car has a ratcheting tensioner.

• Audi 4.2, before and after – This was only 2.5 seconds of chain rattle but the service cost 5800$ according to the owner of the video. It cost this much most likely because in this car,  there are four timing chains, four tensioners and all of it is at the back of the engine.

Apart from the rattling noises, other potential symptoms of a problem with the timing chain include reduced engine performance, a “Check engine” light and error codes related to camshaft timing stored in the car’s computer.

If you’re worried or unsure about the condition of the timing chain in your car, take it to a professional. A more accurate method of checking the chain stretch is to use the engine’s timing marks. The chain stretch is usually measured in degrees (timing shift). A visual inspection of the chain guides or the tensioner may reveal something too.

Camshaft adjuster rattle (VVT cars only)

Cars with variable valve timing (VVT) have special sprockets or pulleys that have a built-in mechanism to adjust the timing of the camshafts using oil pressure. These sprockets are called camshaft adjusters or cam phasers.

The VVT mechanism locks up when there is no oil pressure, for example, during a cold start after a long standstill. The camshaft timing is supposed to be fixed until oil pressure builds up and the VVT can start adjusting the timing.

It is designed this way because the cam adjusters rely on oil pressure to operate. If they don’t lock up properly, the timing goes all over the place until oil pressure builds up.

A side effect of cam adjusters that remain unlocked (because they are broken) is a rattling sound when there is no oil pressure yet.

So, the symptom of a failing VVT mechanism is a rattling, diesel-like noise after a cold start. Ideally, there should be none, but after a long standstill, I would say that a gentle rattle for a second or two is still okay in older cars. Any longer than that and the camshaft adjusters are on their way out. If the rattling is persistent, they are definitely broken.

Click here to hear the VVT rattle. Rattling camshaft phasers aren’t as dangerous as a rattling timing chain, so a brief rattle after a cold start isn’t something to worry about in older cars. If you are worried, it’s best to compare two cars with the same engine and listen if there’s a difference.

However, a persistent noise (like in the video linked above) or one that lasts a few seconds or more means that there is definitely a problem.

Conclusions

The key points to take away from all this are:

• The timing belts or timing chains, along with the supporting components, are one of the most important parts in the engine. Their failure often results in serious engine damage in interference engines (most modern engines).

• Always keep track of when the timing belt needs to be replaced in your car. When the time comes, replace all the critical components, not just the belt. If you are going to buy a used car with a timing belt, find out if the previous owner replaced the timing belt and other key parts on time.

• The typical timing belt lifespan in between 50,000 and 100,000 miles.

• Timing chain vs Timing belt: timing chains last longer than belts, but they are more expensive to replace when they wear out. A well-designed timing chain system can last a very long time but not forever.

• When you get near 200,000 miles, you should consider replacing the timing chain, chain tensioner and chain guides. If the timing system is showing symptoms of wear, it may need to serviced earlier and in some cars, a lot earlier. Do some research before buying a used car with a timing chain – some models are unlikely to get to 200,000 miles without chain replacement.

• If you’re looking to buy a used car, find out if it has a timing belt or a chain. You can find this information in the Car Directory. If the car has a timing chain, look out for any chain noise during a cold start. Timing chain noise is a common symptom of chain stretch or a failing tensioner.

• One last thing – worn out cam adjusters in cars with variable valve timing can also make a rattling noise during a cold start. They are cheaper to replace than a full timing chain kit but rattling noises are a bad sign nonetheless. Better find a car that purrs, not rattles.

If you found this article useful, please share it with your friends!

May the valves and pistons in your car’s engine never meet (it’s a toxic relationship).

The post Timing Is Critical: Timing Chains and Belts appeared first on Still Running Strong.