DriveBy

I have an engine oil leak on my 1996 C-280. It has the 104 in-line 6 cylinder gasoline engine. It would leave a six inch or larger puddle of oil in the driveway each time it was driven. There is always a smell of burning oil and is visibly seen when the hood is popped. The smoke comes from the right rear. The oil is buring off the exhaust manifold or pipe. It has been leaking for over a year but now is getting worse.

I pulled the bottom engine shroud off to look for the leak but now it only drips a few drops, so I'm guessing the engine leaks oil on to the shroud and builds up a puddle there and then drains out the hole in the pan/shroud after the car is parked. I can see some seepage from the front right of the engine but that would have nothing to do with burning oil on the exhaust.

Since I can't get the car up high enough for a good look I took it to a local mechanic and had him look for the leak. He said there was some seepage in the right rear head gasket but not much. He probed the bellhousing with his fingers but found no puddle of oil there, so he ruled out the rear main seal. I don't see any oil around the front pulley damper either.

There is oil on the bottom of the alternator and all over the air pump which is below the alternator. There is oil on the transmission oil line on the front right below the air pump. All the oil appears to be engine oil.

I guess my question is: How is oil getting on the exhaust pipe? And why is it apparently leaking while driving but not when stopped? I've read the archives about the head gasket and the chain cover. Upon inspection it doesn't appear to be that much oil coming from there. I've owned the car 2 years and know nothing of the history of it before then. Can oil be leaking from the chain tensioner? I can barely see it so I can't tell if oil is leaking from there.

Ausmbtech

It's a very common leak on a M103 and M104. The oil feed for the cylinder head is in the corner near the exhaust. The head gasket leaks and eventually needs replacing. Most seep for a while but by the sounds of your leak it's time to replace the headgasket unfortunately.

DriveBy

Thanks for the info. Since the exhaust manifold is above the head gasket, I am wondering how the oil gets on the manifold or exhaust pipe? Does that rear oil leak normally reach the exhaust?

I took the car to another mechanic and he saw a definite leak in the right front but not much in the rear. It seems that the smoke from burning oil only appears when I drive at highway speeds of 60 or more miles per hour. Is it possible that oil leaking from the front could blow back to the exhaust pipe at highway speeds?

Oil does not drip when the engine is stopped, whether hot or cold, or even when it is idleing. If it were not for it puddling on the bottom engine pan/shroud, and then draining out when parked, I would not even know that it was leaking oil.

Ausmbtech

Yep, it's easy for oil to blow upwards, there is alot of turbulance in the engine bay at speed.

Once you need to wash the engine down more often than 6k mi/10k km then it's time to change the head gastket, if it's less often the you can run it a little longer.