I've had the problem with the elbow not fitting, slipping off, etc. I finally just bought a new elbow. Hasn't given me any problems since. That rubber/plastic just gets really brittle and deformed due to its location next to the exhaust manifold and turbo. As far as the oil pooling in the air cleaner, I'm not sure about the W126 box, mine 300D has some around the oil separator, not an extreme amount or anything. The inside of the elbow will get oily depending on the amount of blowby u have.

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1985 300D Gretchen (Astral Silver) 220k
1983 240D 4-speed Evelyn (Orient Red) 203k


TANSTAAFL