Published by Tim Scott on Jun 5, 2015
“My turbo is leaking oil.”
When you run a turbocharger rebuild shop, you hear these 5 words a lot. The next words are usually “I just need my seals replaced.” Hummm, no.
OK, so I figured I would write a post for you guys on this one. First off you didn’t blow the seal out of your turbocharger. Just about all seals are steel piston rings. Some have carbon seals on the compressor side. The carbon seals are originally for draw thru carburetor systems, low mounted turbos, and high pressure crank cast systems. Carburetors would have a high vacuum on the compressor seal. That in return would pull the oil out of the turbocharger. You really don’t have to worry about those systems anymore. Those system died out in the mid 80’s. Some of the SVO mustangs ran them. There are still carbon seals uses today though.
Common Types of Turbine Seals
Ok, let move on to the turbine seals. Now, there are a few different types of seals for the turbine shaft. Most popular is a single gap steel piston ring. Works great has been for years. Things that it does not like, high crank case pressure, low perched turbos, too much oil pressure. How many of these will blow out that seal???? NONE!!! Next seal is the gapless ring. You can do this two ways. Run a piston ring with a labyrinth lock for the gap. Or you can stack 2 rings back to back then offset the two gaps. This is very popular in the Porsche cars. A lot of those cars run 6 bar of oil pressure, low turbos, and sump pumps. For a true seal, the best set-up is two gapless rings in separate grooves. This will seal very well. There is a down side though. By the time you notice its leaking there is not much hope for a cheap rebuild.
Things To Check If Your Turbo Leaks Oil
Ok, back to the topic of the leaky turbocharger. If your turbo has been fine for years and it starts to leak. You need to look at a few things. First off check shaft play. There is always a little side to side. But, it shouldn’t touch the compressor housing. Next check the in and out play. You really shouldn’t feel much at all. If you do, you are in the beginning stage of thrust bearing failure. All of those can be fine and still leak. You can have carbon failure. That is when burn oil has cut up the steel on the turbine shaft. That makes the groove too big for the seals to keep the in the oil. This is the most popular failure I see in the small frame turbochargers. Next you should check crank case pressure. A bad PCV system can make the turbo leak. Also to much piston blow by. Why can these two reasons make the turbo leak? Well, it’s as simple as blocking off the oil return line on the turbocharger. The return line is connected to the crank case. The piston blow by back tracks up the return line. It will then push oil through the seals. And the seals are more designed to keep turbine and boost pressure out of the crank case.
Do You Have Questions?