Oil leaking around oil fill cap.
 

I have been trying to solve an oil leak issue on a friends car.
Its a 1985 300SD.
Odomoter does not work but a goood guess is the car has at least 250 thousand miles on it.

It leaks oil around the oil fill cap on the top of the valve cover.

We have tried several different caps, three of them were new.
And I have made sure the vapor canister in the breather is not restricted,
or the lines to and from it that connect to the valve cover and the oil pan.

The car does not have much blow by.
I can cover the vapor line port on the valve cover for 8 to 10 seconds before the
engine starts to die.

The valves have been set and rechecked twice.
Valve seals do not seem to be leaking.

What would you guys check next ??
Thanks.

Put wheel bearing grease on the seal.

I have the old metal cap, replaced the rubber gasket and no leak. can be bought from Dr.Phill.

It might be the 2 tangs under the cap are tweeked some and the cap does not fit tight.

maybe bend them in a little for a tighter fit?

Charlie

I have also heard that on the metal caps, when you remove it, if you are holding it upside down, the oil on it will run to the outside of the rim on the cap and then when you turn it right side up, this oil leaks out. Not sure if it is true, but it makes sense to me and I usually notice more of a "leak" around my cap after I have removed it for some reason or another. If I wipe up the oil without removing and flipping over the cap, no more leak.

Buy a new cap from you local MB dealer.

Try this first...
 

It's silly, I know, but it works: take off the oil cap you have, use a lint-free shop towel to thoroughly dry the cap's gasket of all the oil as well as the aluminum filler neck (where the cap will fit). Make sure both are bone dry and then re-install it. It helps on mine (at least temporarily)...

Good luck -
James