Recently I rebuilt the M102 engine in my 1988 190E 2.3
Ever since that time I have been losing oil...quite a lot actually.
Well, I finally investigated this and found that the leak was around 3 of
the oil pan bolts on the driver's side of the engine about midway between
front and back of the engine. I actually found one bolt missing entirely!
After replacing that bolt, and retourquing the bolts I could reach, I
degreased the pan and took it for a long road test. To my horror, the leak
did not stop! In fact, it is JUST as bad as before with the missing bolt!.
This leak has a distinct pattern to it: streaks of oil form on either side
of these three bolts and run down the pan. These bolts have been tightened
down as much as I dare, and there was a new gasket installed when I rebuilt
it. I don't understand why it leaks here. It sure didn't leak like that
before it was rebuilt.