Today we have a Mercedes M-Class, chassis 164, diesel engine 642 V6 with an oil leak.
The car has been stationary for a few hours, and a fairly amount of oil has already leaked under the vehicle. This type of oil leak is a common problem which is sometimes misdiagnosed.
We lifted the car onto the ramp, and we did a thorough inspection of the underneath.
The undertray was very wet, so it was a considerable amount of oil on the top.
We removed the undertray to inspect the engine.
We found a lot of oil on the undertray; the oil leakage is significant, as we expected.
This type of leak on the 642 v6 engine is commonly misdiagnosed as coming from the rear crankshaft oil seal, the oil seal behind the transmission plate because it is an automatic vehicle. From our experience, we know that these oil seals rarely fail.
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Most of the time, the leaks come from the upper part of the engine, in between the cylinder heads. We stripped the top of the engine car to see exactly where the leak is coming from.
We disassembled several components from the engine compartment: the airflow, the pipes, the intake manifold, the intake pipe, and the turbo. It was quite an extensive disassembly to get the space we needed to access this oil leak.
We replaced the swirl valve actuator, which often fails due to oil entering the unit. We also noticed that the engine breather was leaking oil; therefore, we proceeded to replace that as well. and replaced that as well. The turbocharger bracket, which incorporates the return and oil supply circuits for the turbocharger, had a gasket that had to be replaced because it can sometimes cause oil leaks. However, this was not the main cause of the oil leaks. We had to do some more digging to find the right cause of the problem.
We also replaced the silver actuator, which is covered in oil; most likely, the oil had seeped in and would soon fail.
We arrived at the cause of the problem: the engine oil cooler has rubber seals underneath that have hardened and allowed oil to leak out. We cleaned out all the oil and changed the engine oil cooler gaskets.
We also cleaned the carbon deposits on the manifold and noticed that the swirl flaps mechanism was worn and had to be replaced, too.
We cleaned and changed the gaskets of all disassembled components, changed all defective components and reassembled everything. We also cleaned under the engine and did a road test.
Now everything is as it should be. If you want to see the entire procedure of this repair, watch this video: From A to Z Engine OIL LEAK FIXED!
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