Verifying Head Gasket Leak - M103 Engine

[Tassie]

My 1989 300E just came back from a servicing and A/C diagnosis (another topic!)

The mechanic stated that the head gasket is leaking. He slid his finger along the block just under the exhaust manifold and showed me his oily finger.

I'm a little sceptical because the car does not burn any oil, there is no oil in the coolant, and the vehicle runs very well. Is there a more a reputable way to determine the need for a new head gasket? Compression or leak down test? Clean engine very well and monitor? If the head gasket is leaking it is very minor now. But if it is leaking, how soon should I replace the head gasket? Will there be disastrous consequences if I defer this repair?

Thanks again,
Paul

[softconsult]

Usual leak location is passenger side toward rear of engine. Don't know if you have the tools, floor jack and jack stands, to get under the car, but if yes then you can visually look for the leak. Reach up and wipe the area where the head meets the block.

My 1990 slowly leaked for 85,000 miles with no ill effects other than adding some oil during interstate driving.

The leak also could be from the front timing chain cover. Very common.

Steve

[Kestas]

I would definitely get some kind of confirmation before digging in to this repair. Clean the area as well as you can and look for further leakage. If it truly is leaking from that area, you can just as well let it go and wait until it gets so bad that you're forced to do the repair.

When this happens on the 103 it is usually a very small amount of leakage and if all else is well, there's no problem in just living with it for awhile.

Good luck,

[oliverb]

My 1990 M103 had oil leaking in the same area you described plus some running down the back of the engine. Had a safety inspection at the local MB dealership and they called me back to see the leaks from under the car. The mechanic told me the very same thing you were told. No oil in the coolant, no oil consumption. I asked about a leak from the valve cover. He said no, head gasket failure. Very close inspection by me later showed oil clearly leaking from under the valve cover on the passanger side (between the exhaust header pipes) as well as from the back of the cover. Less than $10 for a new gasket, removal of the cover plus thorough cleaning of all areas produced zero leaks for the past two years! I still have a very slight leak at the front timing chain cover - most do. It has already been re-sealed once by the dealer 10 years ago but this time I will do it myself. Think I can do a more effective job. I expect to have to do a head gasket job eventually, but not before it's time. Currently at 97K. Hope it hold out for another 20-30K, then I won't feel bad about a complete valve job.