Well I have been working a problem for the last couple of weeks, not very seriously but working it.
There appears to be around the turbo oil return line and air filter oil seperator return line at the upper oil pan in the 300TD, a oil leak.
Also in the air filter is a accumulation of oil. The oil is on the inside, filtered air side, of the air filter, not on the outside, fresh air side, of the filter. So its probably coming from the oil seperator that the PCV system uses.
The blowby when disconnecting the vavle cover to air filter line is not excessive.

I have done the following.

Replaced turbo oil return tube gaskets at the turbo, tube seperation point and upper oil pan.
Replaced the Orings to the air filter oil seperator, upper and lower.
Replaced the valve cover to airfilter tube with the new designed unit, which I have been told, helps prevent a lot of oil from going into the air filter seperator.
Made sure the oil seperator in the air filter is clean, sealed and working correctly.
I vacuum tested the air filter oil seperator drain line, check valve. In the upper oil pan is a check vavle that is supposed to prevent oil from being sucked up into the air filter. THIS TEST FAILED. I tested it by using a Mityvac. Used some ribbon chaulk around the large drain tube opening to seal the rubber hose of the Mityvac. I could not hold a vacuum. IS THIS TEST METHOD CORRECT? Or does anyone know. This definatelly could be the problem. The Tech at the dealer, who is reliable, has never had to replace one of these.
Replacing the check valve requires removing the oil pan.

I will also adjust the valve and install a new valve cover gasket. A little seeping at the valve cover, but not alot.

My main question is on the oil seperator check valve test. Has anyone done this and what are the proper test proceedures.

Dave

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1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car

I thought there was supposed to be a check valve where the oil separator line feeds into the upper oil pan (internally). However, when I questioned Whunter about this, while he had the line out to replace the grommet and o-rings, he stated that there was not a check valve in the lower line. Is this check valve in the upper oil pan maybe? I don't know.

I do know that when I ran a length of wire into the separator drain and then some motor flush at the next oil change, it seemed to cut down on the oil in the air filter area.

Maybe someone here who has had this apart can solve the mystery.

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Sam

84 300SD 350K+ miles ( Blue Belle )

Wash it all off with degreaser and put some dye in the oil. Then look with a blacklight and you can see where it is coming from.

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01 Ford Excursion Powerstroke
99 E300 Turbodiesel
91 Vette with 383 motor
05 Polaris Sportsman 800 EFI
06 Polaris Sportsman 500 EFI
03 SeaDoo GTX SC Red
03 SeaDoo GTX SC Yellow
04 Tailgator 21 ft Toy Hauler
11 Harley Davidson 883 SuperLow

I have had a problem with oil draining out my wastegate drain that has been driving me nuts. I too have excessive amount of oil in my air filter housing.

Here is where it has led me:
Today I used a bypass cyclone to run as an oil seperator and frankly it worked terribly, but that is not the point, I completely disconnected the breather tube from the oil seperator to isolate if my oil is coming from teh breather or the turbo.

What I found is that the turbo could not be producing the oil and neither is the blowby (which was my main concern). Now I am not completely convinced that II have found the problem but what I did was
I eliminated the turbo since I have oil in the throat of the intake at the air filter. I don't think the turbo can throw oil back up into the air cleaner housing.
So... I pullled the top off the seperator and completely cleaned it out using a rag. I also cleaned all the oil out of the air filter and the throat of the intake.

I then replaced the top of the oil seperator and drove the car the car hard on a hill climb for about ten minutes.

Low and behold the air filter had fresh oil on the surfaces. I then pulled the top off the seperator and it is covered with oil. No possible connection to the crankcase vent system.

I am thinking that my chekc valve is bad although I have not tested it yet but by the manual it states that the check valve was put into place to stop the system from withdrawing the oil vapors from the pan.

I will test mine tomorrow and let you know my results. What bothers me is I cannot find any info on the replacement of this check valve and by the pictures it indicates that it is in the pper pan but possibly mounted romt he inside. Could be trouble...

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'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique