I noticed on my VW and GM diesels that the crankcase evacuation systems that recirculate blowby gasses to the intake do not have oil separators. They simply have a tube that routes from the valve cover vent to the intake. It seems strange that MB would go to all the trouble of the oil separation canisters and the return line to the crankcase, etc. when an easier alternative exists? Why not do this on our MBs instead of replacing o-rings, dealing with oily filters, etc. I understand on high-mileage engines with lots of blowby this might not be a good thing but both my other diesels use this system, they use no extra oil and have no smoking problems either. Just a thought. 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

I noticed the older MB's, like my '78, and even the later Euro's do not have the oil seperator. I have a 78 and a 81 Euro parts car that both do not have the oil separator.
Asked a local shop about that. They seemed to think this is an EPA thing? Not sure, but it is possible that MB chose this route to handle some of the air emmisions.

Yah, my old 220D's just ran a hose straight into the intake manifold if I remember right.

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past MB rides:
'68 220D
'68 220D(another one)
'67 230
'84 SD
Current rides:
'06 Lexus RX330
'93 Ford F-250
'96 Corvette
'99 Polaris 700 RMK sled
2011 Polaris Assault
'86 Yamaha TT350(good 'ol thumper)

It may be for the purpose of taking the air bubbles out of the oil... to decrease foaming.. which decreases the effective length of oil's ability to lubricate....
Ron Fornier(famous sheetmetal guy) showed how to make one for race cars and that seemed to be the purpose there...

I suspect it is to prevent putting the "oil mist" into the atmosphere AND to recover as much "oil liquid" as possible. The design of the separater is such that it does it's best to separate the liquid from the gas stream. I'm under the assumption that it works better at "cruise" rpm versus "idle".

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Jim

Engatwork,
Since the VW and GM systems are vented directly to the intake manifold and right before the turbo inlet respectively, these locations are post-airfilter I don't see how any oil-vapor would escape when the engines are running?

Leathermang, What? I don't see how collecting a bit of oil that exists in crankcase blowby gas and returning it to the sump has any effect on oil aeration?

I was just thinking that it would certainly be a lot easier to install a hose fitting in the air intake piping pre-turbo and just run a hose from the valve cover right to it. Does away with lots of o-rings, the return pipe and the greasy separator in the air cleaner housing. Just a thought. 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

It CONDENSES blow-by vapor back into OIL which drains back to the OIL SUMP . . . instead of BURNING it . . .

You're all correct. It's an engineering dilemma: where to put the valve blowby? EPA says not the atmosphere, where it used to go. So the easy drill was (and is) to put it into the air intake. But wait: small oil particles entrained in the blowby condense out onto the intake manifold surfaces. If there's a lot of blowby and the intake manifold surface is really cool, then sludge develops and begins to plug the intake (the modern VW 1.9 engine). So then put the blowby into a cool pot, condense out the oil particles and return them to the oil pan. But wait: some of the combustion "gases" stick to the oil particles and end up in the oil pan (for example, EPA calls sulfur dioxide a gas, but it's really a solid particle light enough to float in air a really long time). And we also have another system to maintain. You're the rich guy if you can figure out the best solution.

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daBenz - 1970 220D

I never knew that.

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Jim

I think that it is there to prevent "runaways" or too much oil going into the intake of a Diesel and then burning and actually causing the engine to run on its own oil. I owned a '80 VW Dasher diesel wagon. The origional 1.5L Diesel had problems with too much blow-by to where the car would all of the sudden start accellerating on its own making one hell of a racket and LOTS of smoke! It would do this with no throttle. The only way to stop it was to put the brakes on and slow it down to the point that it would stop running on its own oil.

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My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.

Ah, but check inside the valve cover before deciding an engine doesn't have an oil separator!

My 220D has one, a tubular device inside the valve cover. Otherwise, the oil thrown off the cam would go straight down the intake -- I imagine oil consumption would be pretty high on the road!

The VW also has an oil separator in the valve cover -- it's a metal plate attached above the cam, works just like the old 220D, indirect path.

The cyclonic separator in the later models will actually recover most of the oil mist from blowby rather than burning it, reducing oil consumption.

I suspect the lack of a separator on pushrod engines has a lot to do with the lack of flying oil from the cam -- plently of time for the oil to fall out of the gas stream on the way up from the crankcase.

The VW diesel run-away is a result of plugged oil drains in the head, so that oil collects in the valve cover until it starts to aspriate into the intake. Happened to a budy of mine, he floored his Rabbit to pass a truck on the interstate and it took off, roaring like crazy and blowing a huge cloud of black smoke. He was a quart low when he stopped for gas and figured it out from there,

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

psfred,
I think you are right about the MB not having the oil separator in the valve cover. I know the VW has it and the GM uses a CDR valve. A simple solution would be to mount a GM CDR valve on top of the nipple of the MB valve cover and then run the tube down into the turbo intake hose. There is even a flat mounting boss on the U-shaped intake tube that looks like it was intended to accept a hose barb or bulkhead fitting. Why all the trouble? I hate that silly, leaky troublesome MB separator design. 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

If you go back 30some years in SI's, you'll see quite a few regarding to BLOW-BY on OM636, M114 and M108 engines.