Oil leak at turbo air inlet

[MarkM]

Anyone have any experience with rebuilding a turbo, internal oil seals, etc.? My turbo is working ok.....absolutely no symptoms of problem, however, oil leaks out of the front of the turbo air inlet where the big plastic duct connects. Is this normal to have oil there, or is it getting through seals in turbo. I know there is a rubber ring inside the duct and a band clamp around the outside that can be tightened, but I'm wondering how much oil is normal at the air inlet, or should I think about getting one of those turbo rebuild kits at some point in the future?

Thanks

[engatwork]

"absolutely no symptoms of problems" is the key phrase. Make sure the rubber seals in that plastic pipe are good and run the heck out of that baby. You do not need a turbo rebuild if you can remove that plastic pipe and "spin" the turbo by hand - make sure the engine is off. There are ways to test the suction and/or discharge pressure of the turbo. After testing to confirm I had suction and pressure I totally removed it, took it to a diesel shop that specializes in turbos and had them check it out where it got a clean bill of health.

The oil is more than likely coming from the "cyclone" separator in the air filter housing. I have noticed on my 300D that running it hard on the freeway totally eliminates any oil in this pipe or in the air filter housing. Idling around town red light to red light causes it to build up.

[psfred]

You will need to determine if the oil is from the turbo or from the blowby tube. You can disconnect the blowby tube or hose for a short time (you will know immediately if you have excessive blowby!) and then check the turbo for oil.

If you have oil leakage, the bearings in the turbo are shot, but if it still spins easily without any roughness, new bearings and seals will fix it -- about $400 at any diesel injection/turbo service shop. They aren't rare these days, and MB uses common manufacturers (Garret, for instace), so parts are readily available.

If you "just drive the hell out of it" with leaking seals, you will quickly wear the bearing sleeve to the point the body has to be reamed and a new sleeve installed -- this isn't always possible as significant bearing wear usually means the housing is munched, too. If there is any axial play or roughness in rotation, you probably need at least a cartridge ($750 or so) or a new turbo.

Fix it while it is cheap! This isn't a DIY project -- you have no way to check clearance, balance on something that can easily run 100,000 rpm, etc. Let a shop do it.

And please please please DON'T put your hand over the intake to feel the suction -- if you slip and get a finger down in there, the turbo will eat it, and as much more of your hand it pulls in before the tendons tear loose in your arm or it stops. This is NOT funny, you can easily lose your hand -- the turbo will be running about 5-10,000 rpm if you blip the throttle, and weighs about two pounds. Terrific momentum. Please think safety -- a turbo isn't a little battery fan or a toy.

Peter

[engatwork]

Peter - what do you suggest doing with the disconnected blowby tube when you take it off of the separator at the air cleaner? There is no doubt I have some blowby which I would imagine alot of 300D's with 200,000+ miles have. Won't it make a big mess under the engine compartment. The biggest indication I had that this is where the oil was coming from was the residue around the elbow on top of the air cleaner prior to me installing a new elbow.
Thanks for the heads up on testing the negative pressure of the turbo - you are absolutely right in that regard and I have edited my post accordingly. I tested it with the engine at idle and will say it was more negative than a normally aspirated engine. Sometimes I forget the experience level of posters. That turbo can pull in some air - along with anything else that gets in that opening.

[psfred]

Jim:

A tin can lightly stuffed with rags will trap the vast majority of the oil mist for short periods. It will also give you a good idea of how much oil is getting carried out and into the turbo from the blowby.

I wouldn't drive it this way for more than a day -- the turbo will spin off any oil from the blowby very quickly. If you drive it to work and back with the blowby tube off and the turbo is still oily, my guess would be a leaky seal. Otherwise, it's blowby and you can ignore it until your oil consumption goes too high.

Peter

[be459]

If the turbo is leaking oil, most likely, you will have black smoke from the tail pipe during acceleration (look for the smoke during daytime, not at night).

When oil going into the turbocharger's oil cage is faster than the oil coming out (thru the oil return tube to the oil pan), oil will leak thru the seals. The seals are metal rings and they are doing a poor job of stopping oil leak. If the oil is overflowing in the cage, a good seal will not stop the oil leak.

Two reasons can cause oil overflow: 1. Oil return tube clogged. 2. Worn out bearings.

In order to do a good seal job, you really have to be sure there is no excessive clearance between the tunnel (which houses the bearing), bearing, and the axial and do not rely on new seals to stop the leak.

A complete turbo rebuild kit, which is about $100, comes with standard size bearings . Sometimes, the "tunnel" wears out and you need to ream it and put in an oversize bearing. The best way of DIY is to take apart the turbocharger and take the oil cage and the axial to a rebuilder to have it check/repair so that you can get the right size bearings.

David

PS: Reread MarkM's post stating that the oil leaking from the front. That may not be the oil from the turbocharger. Oil usually leaks from the back side first since the back bearing is lower.