Published by Tim Scott on Dec 16, 2015

Does your new turbo leak oil but you don’t know why? Check out our video explaining why you may have an oil leak after installing a new turbo and how to prevent it.


Hey guys. Thanks for joining me again. This is Tim’s Turbos on the YouTube channel.

I have been getting a pile of calls these days for new turbochargers leaking and the reason is that new turbochargers don’t leak. It’s always an improper setup.

I’ve yet in the entire time of getting turbochargers new and used have found a faulty brand new turbocharger with the wrong oil seals in it. So, I’m going to go over the basic stuff. I got a bearing housing that I sliced in half so you could see the whole oil passage and where everything goes.

How Oil Feeds Into a Turbocharger

If you look in here, everything red is basically where all the oil pressure is going to be. So this is the cross-center section, this is the oil feed line, and this is where it feeds into both the journal bearings.

Right on the edge here, there is a gap between the oil seal, which is the blue part on each side, and a piston ring sits in here. When the oil fills up the bearings, it comes off the bearings and drops off into this void.

The Bearing Housing Components of a Turbocharger

This is just a void filled with just gravity – there’s no pressure whatsoever on it – so once it falls off the shaft there’s really no pressure touching the seals whatsoever.

So I got to pop in a shaft here so you can kind of see where the oil feeds in. Here’s your piston rings right here and again once it comes out of there, it drops off. The same with on the thrust parts – once everything comes off, it drops directly back out.

Where the Oil Flows and the Piston Ring Sealing It In

So, there is no need for any special seals besides a piston ring. Like I said in many other posts before, all these rings are designed to keep dirt, dust, and exhaust out of the turbocharger and out of your oil system on your car.

Why Your Brand New Turbocharger is Actually Leaking Oil

The biggest point here is to tell you why your brand new turbocharger is leaking.

If the Turbocharger is Tilted, Oil Will Start to Pool

Well, for one thing, the oil return line is the biggest culprit. If you have your turbocharger cocked in any direction over about 15 to 20 degrees, you’re gonna start pooling up here and that’s going to get to the actual oil seal on each side and it’s gonna fill up the cartridge too fast so that it can’t drain properly.

10 AN Fittings are the Wrong Size to Drain Oil

The most popular fittings are the 10 AN fittings for the downpipe or the down drain piece and as you can see – if I can get it close to the camera here – it’s completely the wrong size. It’s only a half inch diameter when you really should have 3/4th inch diameter in there. This is gonna cause an oil problem because it’s gonna fill the cavity too fast.

Use a Pipe System to Drain the Oil

The proper system is to actually use a pipe system and you can use some type of tubing and clamps. Pretty much almost all OEM manufacturers use tubing. It’s very rare that you’re gonna see fittings on there and if there are, they’re gonna be 12 AN size and plus.

As you can see in there, the pipe fitting matches exactly the port. This is gonna be the best way to flow all your oil.

I’ll try to keep it short and sweet. All these fittings that you buy at every shop in the world: they’re wrong. Do not use these, they’re just gonna cause you problems. This is the reason most people use oil restrictors: to correct a wrong problem.

Don't Use These Fittings

When you first put on your turbocharger you want to make sure that this oil feed line is always at 12 o’clock. If you push it over 20 degrees this way or 20 degrees that way, you’re gonna pool up like we talked about over here and you’re gonna have oil problems coming out the turbine or the compressor seal. That goes the same way with the same manifolds that are built incorrectly, pitching forward or pitching back towards the turbine.

Now this is set up for journal bearing style turbochargers which use a lot more oil. You can get away with a lot of this by using ball-bearing turbos in different directions. It doesn’t mean it is set up right, but you can get away with a lot more angle on that.

This is 10 AN. This is gonna be too small – you can’t even put your finger through it.

All the 3/4 stuff – you can put your whole finger through them.

This is a 12 AN Fitting

This is 12 AN fitting. If you’re gonna use AN, this is the one to use. There are plenty of manufacturers that do it. It costs more money, but it’s cheaper in the long run because you’re not going to be replacing turbos for no reason.

Hope that all helps out. Thanks!