Smoke from exhaust

[Fender8024]

Hey guys I just recently redid some stuff on my car gaskets, wiring harness, vacuum lines and cleaned up my bay really good but now that everything is back together my car is smoking like no other as soon as you shift when the turbo releases pressure…I’m thinking it’s my seals on my turbo but could it also be anything else? 1986 porsche 944 turbo stock k26

[Tom]

Blue smoke when shifting can also be valve guides/seals, but it seems suspicious that this happened right after doing work to the car. Sure you got all the plumbing (vacuum lines, AOS lines, etc.) back in their right places? Too much oil? It's common to get oil in the intake pipes via the AOS, which can result in smoking if bad enough. As a diagnostic step, you might want to vent the aos hose into a plastic bottle or other make-shift catch can (unsealed, open to atmosphere). If the oil is coming from there, it may take a little driving to burn off all the oil accumulated in the i/c and pipes, but it there's no change, then at least you can eliminate the AOS as the source of the oil. At that point, I'd be looking for oil in/at the turbo for bad seals and, absent that, check the valve guides and seals.

[Fender8024]

Thank you so much again Tom I will be looking into this week for the catch can could I make a little T from that hose and connect an extra line to it? I’m a little confused on making the tester.

[Tom]

Thank you so much again Tom I will be looking into this week for the catch can could I make a little T from that hose and connect an extra line to it? I’m a little confused on making the tester.

The AOS (Air-Oil Separator) is the black plastic thing at the back of the motor with the yellow oil cap on top. Among other things, it serves a purpose similar to a PCV (positive crankcase ventilation) system. It allows any pressure that might build up in the crankcase (due to combustion pressures leaking past the rings) to escape the crankcase and get re-routed to the intake track (J-boot) right before the turbo inlet. The AOS attempts to separate out the oil and keep it in the crankcase, while letting the air pressure (and associated emissions) run through the motor to burn. The problem is it doesn't always work perfectly, so some oil invariably gets passed through the AOS and ends up in the intake crack -- i.e., in the i/c pipes and intercooler. Heavy boost and older rings make the issue worse.

So I'd probably start by pulling the i/c pipes out and seeing how much oil is in there, and cleaning out as much as you can. Then, to test if it's coming from the AOS, pull the large hose off the 3-pipe manifold coming out under the front of the intake and plug/cap/seal-off that rubber hose. A dowel or rod or plumbing cap in the right diameter can plug the hose, and then a hose clamp around it for good measure. Then take a length of hose and put it on that pipe and into a bottle can of some kind. This hose/can is just to keep the oily mess from spraying all over your motor, but also will give you an idea of how much oil is actually coming out. Drive around, floor it some, etc. and see what you get. That might help point you in the right direction. I would not suggest a T because then oil would still have a route back to the intake.

Lots of ways to diagnose your issue by the way -- my suggestion is simply how I'd probably start. But ask a 100 hard-core 944 turbo guys how they'd go about diagnosing, and you'll get 100 different answers...

[Fender8024]

Thank you for your response Tom! I was able to try this out and did not receive any oil just smoke inside the bottle…I did go ahead and changed the AOS seals and that hose just to be safe and still no luck. Just massive amount of smoke from the exhaust and by the turbo a lot of leaking oil on the block and under the turbo I’m really thinking it’s the turbo seals but any other recommendations because I really don’t want to take off the turbo it looks like a pain

[Tom]

Is the smoke coming out the back of the exhaust or off the hot exhaust pipes when the oil drips onto the exhaust? Have any pictures? Can you tell where the oil is coming from? Before pulling the turbo (which isn't "that" bad) you might make sure it is draining ok. If the oil backs up in the turbo it will find a way out.... But yeah, I can understand why you think it's the turbo itself, especially if it's leaking from the center section...

[Fender8024]

The smoke is coming from both sides the massive cloud is from the end of the exhaust and it only happens when I shift above 3k RPMs. As for the smoke in the bay it is coming from the oil in between the aos and the turbo section of the motor I’ve cleaned it multiple times to find the leak location but the only way I can see oil come out is when the car is under throttle and by that time it makes a giant mess in the bay and I can’t locate the leak. I did just order the hard hose from the AOS to the motor just to be safe because the rubber is a little burnt but not leaking but I’m wondering if pressure from the turbo is causing it to leak (just doing it to be safe). I did my AOS seals and dipstick o ring just to make sure as well because there was a lot of crankcase pressure and it was shooting oil from the base of the dipstick. At this point I don’t know what else it could be but besides the turbo but I also know these cars can be a headache and I might be missing something and so really do appreciate your help because I would be very lost at this point I did do a Venturi delete I don’t know if that has to play part of anything?

[Fender8024]

I do apologize about not having any photos but for the draining part could it be a clogged hose? I think pelican parts made the procedure look a lot worse than it is to remove the turbo that’s why I got a little intimidated…. I really am lost though even after doing the AOS there is still oil in the throttle body, I/C pipes and such

[Tom]

I do apologize about not having any photos but for the draining part could it be a clogged hose? I think pelican parts made the procedure look a lot worse than it is to remove the turbo that’s why I got a little intimidated…. I really am lost though even after doing the AOS there is still oil in the throttle body, I/C pipes and such

It's usually crank pressure that makes it hard for the oil to drain, or too much oil flow. But with external leaks from the turbo itself -- assuming that's not coming from the mount or oil fittings -- then you probably need to take the turbo off either way. You can take the j-boot off and see how much play there is in the shaft. If it's totally toast, it might be obvious. There's tons of collective experience removing turbos on this board, so there's almost nothing we can't help you get through in terms of the R&R. It's not really that bad.