W123 617.952 Non-CA Air Cleaner Oil Separator Sealing DIY
 

My 300CD has no oil loss over an oil change interval. It doesnt have enough blowby to move the cap at all when running, but the oil mist doesnt very effectively separate in the valve cover. What happens as a result is that it eventually collects (in my case) in the turbo U-tube and leaks out onto the wastegate because the seals get very hard and therefore don't seal well.

Tools:
Ratchet with 10mm socket
Flat blade screwdriver
Black oil-proof RTV

What you get is this:

http://i83.photobucket.com/albums/j3...Y/IK3_9840.jpg

http://i83.photobucket.com/albums/j3...Y/IK3_9841.jpg

http://i83.photobucket.com/albums/j3...Y/IK3_9842.jpg

http://i83.photobucket.com/albums/j3...Y/IK3_9843.jpg

http://i83.photobucket.com/albums/j3...Y/IK3_9844.jpg

http://i83.photobucket.com/albums/j3...Y/IK3_9845.jpg

http://i83.photobucket.com/albums/j3...Y/IK3_9846.jpg

http://i83.photobucket.com/albums/j3...Y/IK3_9849.jpg

Others will sometimes get oil in the air filter element itself, I suppose if the blowby is too bad or the leaking from the separator is too leaky.

Some common things that one sees are:

http://i83.photobucket.com/albums/j3...Y/IK3_9834.jpg

http://i83.photobucket.com/albums/j3...Y/IK3_9835.jpg

http://i83.photobucket.com/albums/j3...Y/IK3_9836.jpg

http://i83.photobucket.com/albums/j3...Y/IK3_9837.jpg

http://i83.photobucket.com/albums/j3...Y/IK3_9839.jpg

What I see is that the separator isnt separating properly. Instead a lot of mist comes into the U-tube.


http://i83.photobucket.com/albums/j3...Y/IK3_9838.jpg

Now, why am I sealing the separator? Because mine was loose, and I thought that perhaps there was enough "slippage" of air that there wasnt enough centripetal force to get the oil separated on the walls of the unit. What's the worst that could happen???

The first thing to do is remove the air filter assembly and then remove the right-angle vent tube from the separator assembly.

http://i83.photobucket.com/albums/j3...Y/IK3_9884.jpg

Then, take the flat blade screwdriver and pry up the two bent metal tabs that hold the cover down.

http://i83.photobucket.com/albums/j3...Y/IK3_9885.jpg

http://i83.photobucket.com/albums/j3...Y/IK3_9886.jpg

Then remove the cover.

http://i83.photobucket.com/albums/j3...Y/IK3_9888.jpg

http://i83.photobucket.com/albums/j3...Y/IK3_9889.jpg

http://i83.photobucket.com/albums/j3...Y/IK3_9891.jpg

The product to use is RTV black, the oil-resistant variety.

http://i83.photobucket.com/albums/j3...Y/IK3_9892.jpg

Apply this to the cover and to the lip on the separator body.

http://i83.photobucket.com/albums/j3...Y/IK3_9893.jpg

http://i83.photobucket.com/albums/j3...Y/IK3_9894.jpg

Press the cover down hard and then bend the tabs back to keep the cover tightly in place. Remove any waste excess RTV from the assembly that may have been squeezed out when putting it back together.

http://i83.photobucket.com/albums/j3...Y/IK3_9895.jpg

I would recommend replacing the two oil seal rings on the U-tube. THey should be part numbers:

Intake Pipe Seal OES GENUINE W0133-1635476
Turbo Seal Ring air Cleaner Hose To Turbo. OES GENUINE W0133-1634936

They can be VERY hard and require a good deal of force to crack them and break them enough to get them out of the U-tube.

Re-assemble as you would put the air cleaner back together. The U-tube is attached to the air cleaner and then that is connected to the turbo.

Done!

So how's this separator supposed to work again? I was surprised to see it empty.

In your case, where does the vapor end up going after you've sealed it?

I was too. I think it is really to just have enough surface and volume to slow down the typical blowby airflow rate to allow the mist of oil to slow down, combine and just gravity settle down the drain. I guess the airflow going through maybe helps provide a bit of positive pressure that combined with the gravity-force of oil in the tube, lets it drain past the check valve.

I was thinking if I should stuff something like steel wool in either the tube, separator, etc., but I wouldnt want it to saturate and cause air pressure buildup... I dont know enough about the design of oil mist separators to stuff it properly.

I figure removal even with the RTV in there would be easy enough if there is a better option...

The sealing really just prevents excess blowby air from escaping out the cap and instead flow as it was intended. The vapor will hopefully more easily combine, the air will go the direction it was intended (into the U-tube) and the combined mist (now more of a liquid) will just gravity drain down the tube to the oil pan.

Cool, I want to try this...the wagon has several of the symptoms you did such a great job if photographing!

Did you notice any change in performance?

I've done this on MANY of the turbo cars. it does keep the air cleaner free of oil, unless the blowby is severe. it will not however eliminate the oil from the turbo. but it will cut down on it. no improvement in performance though!
in addition to changing the seals in the "U" tube, it's a good idea to replace the 14mm o-rings in the bottom of the separator and the end of the tube that connects to the separator sits on a nipple in the oil pan. follow the bent tube and you should see what I mean. it should also be bolted to the back of the exhaust manifold, so if yours is wobbling around, it's either broken the bracket or lost the bolt.

No change in performance, but the wastegate isnt oily yet (thus not dripping down). That is likely due to replacing the big seal rings on the u-tube though... Not sure if it is better or worse... since it means more oil in the turbo.

Though the engine uses no oil so it cant be an appreciable amount.

Need to drive it a few hundred more to see what happens...

Any change in oil consumption, JHZR2?

I just did this today. The cap to the separator was rattling a lot, so I hope this will fix the noise and my oily air cleaner. Thanks for the write-up and great pics.

Never had a consumption issue... Loss was low enough that it was a matter of maybe a cup or two over the oil change interval. A cross-country trip yielded no change on the dipstick.

My issue was that I was getting a mess all over the lower part of the turbo u-tube and it was all over the wastegate.

It is far cleaner now, though it still looks like there is an oily coating that has some pooling in the u-tube...

Sorry for bringing this thread back up I just wanted to clarify a couple things for people.

1: Sealing the cap is a good idea for reducing oil seepage into the rest of the air cleaner and I encourage everyone to do it. Not sure why there wasn't a type of gasket there from the factory.

2: How the separator functions? The separator works by having the walls of the unit cooled by the coldest available air source (the incoming air) so that the hot gasses and oil vapor will condense on the inside walls, and run down into the oil pan. Now I am against stuffing the unit with steel wool as it reduces the available COOL surface area, therefor reducing the amount of oil condensation, encouraging the vapors to blow through into the intake, and steel wool doesn't encourage draining so well. Now if you were somehow able to get an aluminum or copper type wool, the conductivity of the metal might negate that problem.

It will not reduce the ability to cool, I disagree with that. Lots of work has been done in cooling chemical reactors and how packing with the right wall contact does a better job.

Having a high conductivity (metal) packing with good contact to the outer edge would enable more cooling surface in the middle of the gas path. IF condensing junk out was desired, this would do a better job.

Im not convinced that "condensation" is actually what they are going for. The moisture and fuel vapors from blowby would be better off re-combusted.

The issue is how to get the oil mist that is made from the camshaft and under the valve cover knocked out so it isnt combusted and/or getting into the turbo and intake.

The key to doing this is a gas path that helps to cause the mist to agglomerate and settle. You want this to happen in the tube or the separator. You dont want oil mist going back into the intake air path at all (which is why a 240d and others have them), but particularly when the EGR is present due to the soot load.