Hello,

I recently purchased a 1983 300D, yellow, 173k miles. The car is in very nice shape inside and out. It does need some work mechanically, which is the reason for this post.

I pulled the air cleaner housing to clean underneath and check the condition of the turbocharger, and I found that the oil return tube from the air cleaner was missing. There's a fair amount of oil on the turbocharger, head pipe, and engine mount area. The air cleaner element itself was also filthy, and the housing had a good amount of oil inside. I figured someone had removed/lost the tube, no big deal, easy to replace. However, I began searching for the nipple where the tube outlets into the oil pan, and it is not present. I believe it is usually situated right next to (driver's side of) the turbo drain tube, and it's not there. After researching, I'm beginning to think the motor was swapped for a 1985 edition (I live in California), and the manifolds from the pre-85 were mounted onto the 85 engine. I have no records of the swap, but why would the oil return nipple be absent ? None of the other components from the 85 California engine are present as far as I can tell.

My questions are:
Is there a way to identify the engine by year ?
Were there any 1983 om617 motors that did not have an oil return from the air filter housing ?
How can I properly vent/return the oil from the air filter to the crankcase ?

Thank you for any help/thoughts.

Wallace