Most Common Mercedes OM642 Engine Problems and Failures

The OM642 is a six-cylinder diesel engine developed by Mercedes-Benz, manufactured from 2005 to 2021 in Berlin and Untertürkheim. The engine was first deployed in the Mercedes C-Class W203, and later in almost all other Daimler models in the higher price ranges, in some transporters, as well as in models from the brands Chrysler and Jeep.

Mercedes OM642 Engine Problems

The OM642 has a number of weaknesses that can lead to costly repairs. Below we have compiled the most common flaws for you.

Problems with the Exhaust Manifold

Due to extreme heat, the exhaust manifold may suffer material damage and become leaky. As a result, particles can become dislodged and enter the turbocharger, potentially leading to its failure.

Leaky Oil Cooler

After years of use, the oil cooler may require a new gasket, a change that is associated with a high labor cost. If there is always a small puddle of oil under the car, the gasket is probably already worn out and should be replaced promptly..

Defective IMRC (Intake Manifold Runner Control)

The Intake Manifold Runner Control (IMRC) may suffer a defect sooner or later. This is often due to oil dripping from the turbocharger into the component.

If only the actuator is defective, a noticeable loss of performance can be detected at low speeds, and the engine is usually put into emergency mode. In addition, the plastic linkage may break. The cost of repair is generally in the four-digit range.

Defective Turbocharger Boost Controller

The turbocharger's boost controller may suffer a defect, leading to engine stuttering during partial load, and a noticeable lack of performance.

Defective Crankshaft Main Bearings

In some cases, the crankshaft main bearings have given up prematurely due to material weakness, leading to a catastrophic engine failure in the worst case. Mostly affected are older examples, particularly up until the 2009 model year.

Diesel Scandal

Illegal defeat devices to manipulate emission values have been detected in the OM642, resulting in a recall of all Mercedes models with this engine. During the workshop visit, a software update is performed to eliminate the software.

Before purchasing a Daimler with the OM642, it is essential to check whether the recall has been carried out. If not, this should be done to avoid the vehicle's deactivation.

Carbon Deposits

Soot build-up on the injectors and in the EGR valve can lead to costly repairs, particularly in diesel vehicles, and the OM642 is no exception. To prevent or at least delay this, it is advisable to use cleaning fuel additives at regular intervals when refueling.

Mercedes OM642 Engine Specifications

Conclusion

At its core, the OM642 is a fundamentally solid engine that can hardly be matched in terms of smooth running and performance. While its reliability is generally not bad, there are several weaknesses that can cost a lot of money if ignored.

You should therefore avoid purchasing a Mercedes with this engine if the service book has significant gaps or is missing altogether. If you also don't have the necessary funds for potential repairs, you may be better off with the more maintenance-friendly and cheaper to maintain four-cylinder series OM646.

Cars That Are Equipped With Mercedes OM642 Engine