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matsuzaka's Avatar
 
Join Date: Oct 2008
Location: Cincinnati
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Bad turbo seal cause smoking all the time?

I have an intermittent smoking problem with my 86. It could be that my turbo seal is bad and that's why I'm asking if that would cause smoking all the time.

I always let my car idle for a minute, at least, before I shut it off. I drove the car to work one day and was letting it idle when I noticed a good amount of smoke in the mirrors, got out and the smoke was coming out of the tail pipes. I took the IC off and there was some oil around the flange on the pipe that connects at the IC, the turbo housing was very clean and dry. I assumed that my turbo seal has gone bad. I drove it home several hours later and this time, as I let it idle, it never smoked. It has been the same case since that time, sometimes it smokes and sometimes not.

I've read some of the threads regarding this type of problem and am wondering if it's not some kind of restriction in the scavenge system, that's why asking the question. I owned an import car parts business for 25yrs and I remember reading that to always check the oil return hose/components when a turbo car is smoking. Some turbo remanufacturers insisted that the return lines be replaced when installing a new turbo.

Your thoughts would be appreciated.

Old 10-21-2010, 05:22 AM
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HoyaBear
 
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Had a similar problem with my car, it could be one of several issues, but most likely it is something pretty straight-forward. I would start as such:

First, what idle speed is your car running at when smoking? If the idle is too low, the scavenge pump won't be driven fast enough to clear the oil out of the drip tank.

Second, I'd check the lines going from the drip tank to the scavenge pump. Disconnect the line where it goes into the pump and then disconnect from the other end. Shoot compressed air (or blow really hard if you don't have a compressor) into the end of the line nearest the turbo and see if any coke particles come out of the other end. If you find nothing there, you can then check the other line (going from the pump to the oil tank) although it would be less likely to find the problem here.

Thirdly, if you still haven't found the root of the problem, try rebuilding the scavenge pump (you can buy a kit from TurboKraft).

If you still are having problems after doing all of the above, conduct an oil scavenge pump test like so (YouTube - Scavenge Test Idle @ 1,050 while running hot after 20 min 2, 2 5 and 3K RPM) and this can help you better understand what conditions are causing oil to backup into the turbo. If the scavenge line doesn't suck up oil as fast as it comes out of the drip tank, there is a problem (as you can see happening in this video after 3K RPM).
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'86 930: 3.4 Andial build, Web GT2 Evo cams, Carrillo rods, ported/polished heads, MSD 6530, B&B headers/exh + intercooler, K27HF, 1 bar spring, Tial wastegate, Andial FE, Lindsey Fuchs. Back in black!!!
Past:997S cab; '88 930; '86 951; C5 Vette; 4th Gen Z28; 3rd Gen Trans Am GTA; '71 Z28
Old 10-21-2010, 08:42 AM
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Smart quod bastardus
 
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Great advice above by hoyabear.
In addition to this test it could be the seals in the turbo. Does this happen only after running high boost for prolonged periods? If so this indicates faulty turbo seals. I had a similar issue that only saw very bad smoking at idle on restart after heavy track use at DE events. During the run there was no smoke only at idle after the car sat between sessions and restarted. Was bad turbo seals.
Try pulling the air filter housing off and seeing if there is lots of oil inside the housing. This would be coming from the crankcase vent lines which indicates oil blowby the piston rings. This would make its way down into the inlet side of the compressor housing. However you mentioned the inlet side of the compressor is very dry so the only way for oil to get in the exhaust system now is thru the exhaust bearing side of the turbo center section or from leaking valve guides.
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---"When you're racing it's life! Anything else either before or after, is just waiting"
Old 10-21-2010, 09:22 AM
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Turbofrog
 
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If you have BB headers check the return line for kinks. I had the same after a track session and it turned out to be a kink in the hard return line.
Old 10-21-2010, 10:12 AM
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Hoyabear,
I saw and read your 6 page thread about your smoking problem. My symptoms are a little different than yours, however, I'm going to check the scavenge line, it makes sense. The previous owner had the car for eight years and only drove it 8K miles and I think he ran regular oil and not synthetic so coking potential is there.
Old 10-21-2010, 01:51 PM
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So, if the seal in the turbo is bad it wouldn't necessarily smoke all the time? That's what you're saying, right, fredmeister?

Any other opinions?
Old 10-21-2010, 06:29 PM
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Smart quod bastardus
 
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Quote:
Originally Posted by matsuzaka View Post
So, if the seal in the turbo is bad it wouldn't necessarily smoke all the time? That's what you're saying, right, fredmeister?

Any other opinions?
Yes, my seal was marginal on the street driving because you were not under constant boost for extended periods like on track. After a 20 minute track session and the car sat and cooled off for 1.5 hours, upon restarting it was like a fog machine for about 3-4 minutes at idle until it cleared up. It also did not smoke while on track.
you really have to investigate one item at a time to make sure they are functioning properly. Process of elimination. In the meantime this is educating you on the function of each component of the system.

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1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"
Old 10-26-2010, 01:00 PM
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