I put my money where my mouth is and disconnected my oil separator on my 300D. Why you ask? Well the shaking at idle had broken the separator return tube. That tube is $60. The rubber grommet in the air cleaner lid fits so loosely around the inlet to the oil separator that it was allowing grit into the intake. I have tried in vain to get another grommet, no dice, from Phil or the dealer. I capped the return bung on the oil pan. I closed of the top and bottom of the oil separator in the air cleaner housing. I drilled a hole and put a 3/8" brass hose barb in the flat spot on the U-tube intake right before the turbo. I then ran a piece of 3/8" fuel grade hose from the hose barb up to the 90* rubber elbow from the original vapor vent setup on top of the valve cover. I inserted a piece of 3/8" brass tubing into the fuel line and then pushed the fuel line into the rubber elbow. The brass tubing allow a hose clamp to secure the elbow to the 3/8's hose without crushing/closing it off. No more oily muck in the top of the air filter. After @400miles there is no apparent extra oil use or any other problems. I did this because my two other diesel vehicles have similar setups with no oil separators. Looking at pictures of Euro MB's they don't appear to have oil separators either. IMHO the oil separators were a US emissions thing. So far so good. I would take a picture but I have no idea how to post it. RT

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When all else fails, vote from the rooftops!
84' Mercedes Benz 300D Anthracite/black, 171K
03' Volkswagen Jetta TDI blue/black, 93K
93' Chevrolet C2500HD ExCab 6.5TD, Two-tone blue, 252K

It is not emissions...
Read this thread:
Run away diesel, why does it happen?

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After I read your description, I understand that you no longer have any oil separation. You are basically feeding all the oil and gasses, from the valve cover, directly into the turbo inlet. Sounds like a high turbo wear set-up to me. Especially, when liquid hits the turbo blades at speed. Also, with this scenario, you may run a very high risk of runaway if their is a condition of vacuum in the turbo inlet.

You can check with the pros here. IMHO, sounds very risky to me. Crankcase ventilation is not an emission feature. It is to keep gases from building up in the crankcase.

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Sam

84 300SD 350K+ miles ( Blue Belle )

You now have kinda/sorta the same type set up as a '79/'80 300SD.

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Jim

SDBlue,
You are correct. I no longer have ANY oil separator. First of all has anyone looked inside a MB separator? Its empty with a small diverter to make the incoming crankcase gases swirl around the chamber. There is a vent line that comes out of the top on the opposite side of the chamber top and takes a 90* turn down pointing into the intake. Thats what you see with the air filter top off. At the bottom of the separator there is a drain, by gravity back to the oil pan. The placement of the new fitting in the U-tube will allow the crankcase gasses to be drawn out as a slight vacuum exists in the U-tube from the resistance of the air cleaner and the sucking of the intake/turbo. This will scavenge the crankcase gasses. Regarding oil drops passing through the turbo. This happens already. Look at the oily mess in your existing air filter housing and U-tube. There really shouldn't be "drops" per se but a very fine oil mist. Its not like I am sucking raw combustion gases straight out of the valve cover. There is a baffle on the inside of the valve cover to prevent liquid oil from being sucked out. I have a VW Jetta with a baffle in the valve cover and the vent goes right to the intake manifold. 300+K and no issues. On my truck the valve cover has a hole in it, no baffle, then a push in baffle and the vent line runs right to the mouth of the turbo. 209K and no issues. As Engatwork pointed out, the 79/80 SD turbos had basically the same setup. I looked at one in a junkyard to check it out. Of course if I overfilled the crankcase or if I had enough blowby there is a possibility of a "runaway" engine. If you looked at the stock oil separator I think you will agree that with enough blowby you could have a runaway with that too. I am monitoring the oil use of the engine. Usually it uses almost no oil. I would assume that if my new breather setup allows more oil use I will see it on the dipstick. Since MB did this on stock engines, my engine is in good condition and I don't overfill it with oil I don't forsee any problem with doing this. Part of the reason for doing this was to do away with the nasty oily separator in the air cleaner housing and the grit that has been getting past the seal at the top of the filter. The other reason is that I am planning on a custom intake/filter setup that I am designing. Not having to deal with the separator makes things easier and looks a lot cleaner in the engine compartment, IMHO. There is no "grave danger" in what I have done. RT

__________________
When all else fails, vote from the rooftops!
84' Mercedes Benz 300D Anthracite/black, 171K
03' Volkswagen Jetta TDI blue/black, 93K
93' Chevrolet C2500HD ExCab 6.5TD, Two-tone blue, 252K

That and my 300SD has no oil seperator at all, never did, has no place for one to drain unless you remove the dipstick...............

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1971 280SE W108
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1975 Ironhead Sportster chopper
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"He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche

Hello rwthomas1
This is NOT a gas engine.
The crank case is under pressure at speed/load, gasses and liquid oil are blowing into the oil separator under pressure, plus your alteration adds direct turbo suction.
With your alteration; 100% of gasses and liquid goes directly into the combustion chamber, a sure recipe for disaster sooner or later.
This is an OM617 Mercedes Benz, please do not try to compare it to a VW Jetta, the technologies are not the same.
The 79/80 SD turbo had a different setup, Mercedes Benz is aware of the possible diesel run away problem, I can assure you there is a difference without having the total crank case vent system schematic in front of me for this year model.
I have looked at the stock oil separator, enough blow by on it can cause a runaway, however, it is there to reduce emissions, reduce crank case oil loss and reduce the risk of run away.
Monitoring the oil use of the engine is a poor substitute for the correctly engineered device.
I suggest you ask mplafleur and Larry Bible how much time it takes for an engine to run away and junk out.

If that picture is actually still available anywhere, I'd be interested in seeing this as well.

But as it was origionally posted back in 2004, I'm not holding my breath!

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Testing the cheap Mercedes axiom, one bolt at a time...