Bernstein, Jeff (PSC-Akron)
Jeff.Bernstein at pneumaticscale.com
Tue Oct 3 16:50:35 EDT 2006
Oil can leak on either side of the turbo but you are probably right as to leaking more on the intake side. As you mention below it can leak on the exhaust side but doesn't burn appreciably until you start to accelerate thereby increasing the exhaust temperature.
As to helping to determine the real culprit I would accelerate to about 70-80 MPH while putting the car in a lower gear to decelerate the car for a reasonable long distance. If the valve seals are bad you should see a lot of smoke behind you. If you don't see any smoke then I would suspect that the turbo seals are going bad.
Anytime I have seen a turbo go bad it has started smoking badly when the car sits idling for extended periods of time. It is admittedly difficult to diagnose since our cars don't seem to have a problem with the valve seals or the turbos going bad so it doesn't give you much history to go on.
From: Derek Pulvino [mailto:dbpulvino at hotmail.com]
Sent: Tuesday, October 03, 2006 4:29 PM
To: Bernstein, Jeff (PSC-Akron)
Cc: 200q20v at audifans.com
Subject: RE: Burning Oil???
Ok, so consensus is for two possible culprits in the battle. Apart from
black-box, blind part replacement, how does one narrow down the true
suspect? I'm guessing on your 924 that oil was found to be leaking on the
intake side of the turbo, allowing it to migrate into the combustion
chamber? Or was it also a function of the high-heat within the
turbo/exhaust path being able to raise the leaked oil to it's smoke point?
...and as a vote against the turbo-seal option, how would turbo-seals result
in extra smoke on startup? My understanding is that is a classic valve
guide seal problem indicator.
>The oil burning that you are describing sounds like a turbo going bad to
>me. If, as was mentioned in an earlier post, you have smoke on long
>deceleration then I would suspect valve seals. If you don't get smoking
>on long deceleration then it is most likely turbo seals starting to fail.
>The amount of smoke on acceleration after idling sounds like too much smoke
>for a valve seal problem to me.
>The smoking on long idling is exactly what would happen on my Porsche 924
>Turbo and my Audi 5000CS Turbo when the turbo seals were failing.
>Apparently when the car idled for any length of time with the oil pressure
>being very low it would allow a lot of oil past the seals. As soon as you
>accelerate you burn the excess oil out of the turbo at a fast rate which
>makes a huge cloud of smoke. Under normal running conditions the oil
>pressure was sufficient to keep the seals from leaking on the turbo.
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