Mercedes-Benz 190 (W201: 1982-1993)

M102 engine – single-row timing chain

The early M102 engines were originally fitted with single row timing chains, and there have been cases of premature failures.

In my opinion, any M102 engine with a single row timing chain should have the chain and tensioner replaced every 100k miles or earlier if the chain becomes noisy. Neglecting to replace these parts can result in serious engine damage (valves hitting the pistons).

Mercedes-Benz updated the M102 engine to receive a double row timing chain in 1988. These chains are a lot tougher, and under normal conditions, should last the “lifetime” of the engine. “Lifetime” can be very roughly defined as 200k miles.

The above also applies to the 2.3-16 Cosworth engine. The 2.3-16 engine had a single row timing chain just like the standard M102. Only the newer 2.5-16 already had the updated duplex chain.

M102 & M103 engine – head gasket failure

The head gasket is a weak point in these engines. Considering head gasket replacement is inevitable at some point, often in the 100k – 150k miles range.

Before the gasket fails completely, these engines often develop an external oil leak from the head gasket at the back of the engine. Make sure to inspect that area when buying one of these cars.

Once the head gasket fails and is replaced, the new one should be good for another 100k miles. This issue mainly affects the 6-cylinder engines because of their long cylinder heads. The 4-cylinder engines are also affected but to a smaller degree.

If you’re curious why the head gaskets fail more often in the inline-6 engines – it’s because of the difference in thermal expansion between the cast iron engine block (11 m/m.K x 10^-6) and aluminium alloy cylinder head (22 m/m.K x 10^-6).

As you can see, the expansion coefficient is two times higher for aluminium. This means that when the parts get hot, the aluminium cylinder head expands twice as much as the iron block. The longer the engine, the more pronounced this effect is. The head gasket, which sits between the engine block and the cylinder head, has to deal with these expanding parts.

This was a relatively new engineering problem to solve at the time as former Mercedes-Benz engines had cast iron cylinder heads. Aluminium alloy started being commonly used in the 1980s to make lightweight cylinder heads. These days, the engine blocks are also made out of aluminium alloys.

M102 & M103 engine – KE-Jetronic fuel injection

The M103 and some M102 engines were equipped with a mechanical, Continuous Injection System (CIS) called KE-Jetronic, which was designed by Bosch. The system itself is well-engineered and reliable.

The problem is that most repair shops these days are clueless as to how this system works. Unless you can find a specialist or you understand it yourself, trying to get a KE-Jetronic problem solved might not be easy.

If you find a car that runs well, it will most likely keep going as the injection system doesn’t require any special maintenance. However, if it does break down, it will be trickier to fix than a more modern electronic fuel injection system.

If you already have a car with KE-Jetronic and you are experiencing problems, often they can be fixed by replacing the vacuum pipes as the system is sensitive to vacuum leaks.

Check the following points before purchasing a car with KE-Jetronic:

• Idle quality – The idle should be even when cold and warm. The engine should not die or hesitate when coming to a stop (out of gear in a manual transmission car).

• Power delivery – it should be smooth throughout the rev range. There should be no hesitation when pressing on the accelerator pedal.

• Cold starts – see how well the car starts when the engine is cold.

• Hot starts – when warmed up – shut the engine down for 10 minutes and see how well it starts then. This step is important, repeat it twice.

It everything works well, you should be OK.

Engines with KE-Jetronic should not be run on LPG. It is possible to convert it to LPG, using a second generation system, but it is not a good idea. In fact, I recommend that you never buy a car with KE-Jetronic that has ever had an LPG installation fitted for two reasons:

1. The fuel injection system has a mechanical fuel distributor, which is lubricated by petrol. When you switch to LPG, the distributor will be running dry and start wearing out.

2. With a simple second generation conversion, there is a risk of gas explosion in the intake manifold, which has a large volume. If this happens, you would be left stranded on the roadside with half the vacuum pipes blown off the engine. Even when you fix the car, it will likely never run the same due to the damage that was done (bent air flow sensor plate, damaged vacuum pipes and likely air leaks).

Summary of problems & additional information

• Corrosion is your number one problem with any older vehicle, including this Benz. Suspension, interior and engine parts can be replaced, but a rusted body can be the death of a car. Luckily, the W201 has better corrosion protection than the following generation of Mercedes-Benz cars, which developed a reputation of rusting easily due to the introduction of water-based paint.

• The W201 chassis shares many parts with the famous Mercedes-Benz W124. Both models were designed with longevity in mind. A diesel W201 could potentially be a million-mile car when looked after. Petrol engines are long-lived too. The W201 was given the nickname “Baby Benz” because it was the smallest Mercedes-Benz produced at the time.

• The indirect injection system in the diesel cars is very reliable and relatively insensitive to fuel quality. This is because the inline injection pump is lubricated by engine oil, unlike in modern cars where diesel fuel itself is the lubricant. Many people choose these vehicles for vegetable oil conversions (in countries where it is legal).

• The KE-Jetronic is an interesting piece of engineering and a part of automotive history, but it may be difficult to service. If you are planning to buy a car with KE-Jetronic, make sure the system works as it should.

• Apart from the occasional head gasket replacement, all petrol engines are reliable. With proper maintenance, they can last a very long time.

• The Cosworth 2.3-16 and 2.5-16 are going to be the highest maintenance choices.

• All W201 engines are fitted with timing chains, which normally don’t have a specified replacement interval. The timing chains in the W201 are generally reliable, except for early M102 engines, but they will not last forever. Read more about timing chains.

Petrol engines – specs & performance figures

Diesel engines – specs & performance figures

Petrol engines – technical details

Diesel engines – technical details