Gaining Engine Oil: OM366A Mercedes

[Dave The Hat]

Hi Guys

After a bit of advice.

OM366A engine in a Mercedes 1617.

Last few days she has been belching out exhaust, way more than usual, even when at running temperature, and have been gaining a significant amount of engine oil.

Initially thought it was water getting in the oil as the smoke was a whiteish colour.

However, she is holding her temperature very well, she has not needed any water adding to the header tank, and when we changed the oil there was no sign of water in the sump/oil drained out.

Therefore thoughts lead us to think she is leaking diesel into the oil supply. The oil does appear quite thin, and the oil filter element had a purple tinge to it suggesting diesel contamination.

First thought: injecters not tight, so leaking diesel into oil supply in the cylinder head.

However, all injecters tight, no concerns there. Return line also tight (where it screw into the side of each injecter)

She has full power, drives along fine as usual, but belching out smoke and like we say, gaining oil.

Looking through the Merc manual, I discovered a page detailing the replacement of O rings below where the injectors sit.

So, if you pull out the injectors, you are left with the cavity they sit in. But there is a protective sleeve in this cavity, that can be removed with a special merc tool, and apparently an O ring sits below this protective sleeve.

These O rings do come with the head gasket set, always have done, but I've never acutally replaced them. The manual suggests that if these O rings are old/perished, then water can get into the water supply. But we are convinced it is not water, but diesel.

Do you guys think diesel could get into the oil supply from these O rings? I guess if the injectors are spraying into the combustion chamber, there is potential that it can escape into the oil supply due to these O rings being worn?

Also thought the timing of the engine is wrong so delivering too much fuel, leading to excess diesel in the combustion chambers hence the excess smoke, but we have not played around with the timing on the injector pump, so find it hard to believe this is the issue.

Any thoughts appreciated.

David