In my recent post I detailed how a 1990 300SEL that was given to me had an issue with smoking. It wouldn't smoke at start-up put it would after a few minutes and really smoke under load. After removing the valve cover, I was shocked to find a thick layer of black, tar-like film coating everything inside. I posted some pictures of it. My plugs kept getting oil fouled as well. Of course I dreaded that i might have a blown head gasket , but since the compression was consistent for all 6 cylinders, I decided I had nothing to lose by replacing the valve stem seals myself and along the way remove as much of the tar as I could. I'm very happy to report that now the smoke is all gone, the plugs all have a nice tan color, and she idles nice and smoothly. I just installed a brand new coolant over-flow bottle. No oily ring or milkshake in the fluid! My vote is to change your valve stem seals.

__________________
03 CLK430 Cabrio 211K Pweter Silver/ Oyster Leather
90 300SEL 214k Pearl Black/ Alto Grey/Black Leather

Prior: 85 190E, 88 300TE, 89 300TE, 90 300E 2.6, 90 300TE, 92 300E 2.6, 91 and 93 300SL, 87 Ferrari Mondial Cabrio