272 engine oil leak

[engatwork]

I've got an 08 E350 in the shop with a bad oil leak. I've replaced the breather puck on the rear of the passenger side valve cover and the plugs. Seems to be a substantial amount of oil sitting in valley of the v of the engine. Before I remove intake manifold what is under there on this application that could be leaking oil. Thanks

[paul roberts]

Originally Posted by engatwork

I've got an 08 E350 in the shop with a bad oil leak. I've replaced the breather puck on the rear of the passenger side valve cover and the plugs. Seems to be a substantial amount of oil sitting in valley of the v of the engine. Before I remove intake manifold what is under there on this application that could be leaking oil. Thanks

I've done more than a handful of the vacuum pumps on the back of the engine on the driver's side for leaking oil.

[engatwork]

I'm not seeing any leakage from anything attached to the back of the heads/valve covers but the v below the intake seems to be full of oil. I'll get around to investigating it further over next few days.

[engatwork]

Got it on the lift this evening and based on all I can see it looks like the lower oil pan and oil fill cap are leaking. Will change both over next day or so.

[engatwork]

Looks like new oil cap fixed it. This is not the first time I've seen a new oil cap fix a leak this year model.

[RobertFini]

Originally Posted by engatwork

Looks like new oil cap fixed it. This is not the first time I've seen a new oil cap fix a leak this year model.

Hey, Jim!

My wife's 2007 E350T-4M with M272 has very suddenly begun losing massive amounts of oil (three quarts in 275 miles); some is burning, as I see a thicker cloud than I should on startup that dissipates pretty quickly, but there's a massive leak as well, with oil up on top of the engine near the front, which could be the filler cap as you found in your case.

I've had the car to two different indy shops and neither wants to take the time to figure out the problem, just telling me it needs a new engine. After practically begging the second shop to do a compression test, they tell me all six cylinders are at 150 psi, but are claiming that doesn't confirm anything, as it could be the compression rings are fine but the oil rings are shot. Their theory is that it's blowby pushing oil out the dipstick, but I don't see oil on the dipstick tube and if the compression is good I wouldn't think there should be much blowby. There is also a very ugly cyclical noise from somewhere in the engine compartment that they've diagnosed as a piston slap, but I can't say that I've ever heard a piston slap and don't know whether to agree or disagree with them.

Any thoughts on the subject would be welcome.

Best Regards,
Rob

[Zulfiqar]

Originally Posted by engatwork

Looks like new oil cap fixed it. This is not the first time I've seen a new oil cap fix a leak this year model.

I saw the same on some 273 engines too, One was a dealer maintained car which "needed an engine" because it was too oily outside.

which came to be a split oil cap gasket :facepalm:

some shenanigans are just too much - and I specially see that with original owners of S class cars like this one was.

[RobertFini]

My apologies to all for taking so long to update this thread; the car is located at our vacation house in the Hudson Valley and I haven't been able to spend much time with it this Summer.

Nevertheless, I'm here now and I suspect that the problem was an improperly fitted oil filler cap. The last time I was here (about two months ago), I took the car for a high-revving ride on the Taconic Parkway 20 minutes out and 20 minutes back, holding it in third gear with the cruise set at 64 MPH, so running just under 4K RPM the whole time, and the only smoke we had was at initial startup (but lots of it). During the ride, the low oil indicator came on, but that was to be expected.

This time I added two quarts of oil and did the same thing, and got the same results - plenty of oil smoke on initial startup but then nothing when I went out on the highway at sustained high revs. When my wife initially had the problem, we had just had the car serviced back home but she reported no issues on the four-hour ride up; however, we did have the car inspected after she arrived (it's registered in NY and was overdue), so I suspect they topped off the oil and didn't replace the cap properly.

Thank you all for your input and feedback on this. If I recall correctly, oil smoke on startup is indicative of bad valve seals, right?

Best Regards,
Rob

[engatwork]

Sitting at a red light idling and then accelerating away, with smoke coming out of tail pipe, is indicative of valve guide seals based on what I've read.