Thanks for finding this old thread. I thought that drain tube has a check-valve since I felt it pop open when I blew slightly on the drain tube (via a rubber hose). I wonder if essential. If minimal blow-by, there shouldn't be high air velocity and resulting pressure drop in the PCV tube, so oil mist that is captured into drops on the tube walls should run down into the pan under gravity. It seems the factory design allows build-up of oil in that tube when running, then when the engine is off, the valve will pop open under enough liquid oil "head" to drain down.

My 1985 CA 300D engine has a unique design. There is no oil separator, just a rubber Y which lets oil drops/mist flow directly into the turbo inlet duct. That gunks the compressor wheel. There is no port for an oil drain on the upper oil pan. My 1985 now has an earlier engine, but I kept the frame-mounted air filter (no oil separator). I ran that tube from the Y to the oil drain tube so it doesn't gunk the turbo. I then did the same in my 1984 300D, since I prefer the frame-mounted air cleaner (engine filter brackets shake and break).

Others have plumbed an after-market cone air filter on the turbo inlet. They plumbed the PCV tube to an after-market "oil mist catch can", which many gas turbo tuner guys use (buy on ebay). I assume they drain oil from the catch can periodically and perhaps pour it into the engine (or pour into used oil recycle jug).

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans