Changing Turbo...what I've learned

[b.benz at charter.net]

Derek, 
Oil on the front side of the compressor wheel can only be coming from the crankcase bypass system, as excessive oil entrained blowby. What were your compression test readings again? As a temporary trial, you might try venting the CC breather system to atmo.

Bernie




---- Derek Pulvino <dbpulvino at hotmail.com> wrote: 
> After finishing this project last weekend, wanted to air the couple  
> of things I figured out...
> 
> Most of the bolts were surprisingly easy to both get at and loosen.   
> Those krauts must have used some amazing anti-seize compound or  
> something way back when they made this thing.  Yes, one of the bolts  
> at the turbo to downpipe flange is smaller (15mm vs 17mm), but not  
> tough to get at and loosen.
> 
> The ones that's the bitch is the top left bolt between the turbo and  
> the manifold (as you face the engine from the passenger side while  
> standing up).  It's a 15mm, but access is nigh on impossible.  There  
> is not enough room to get a socket, or the closed end of an end  
> wrench on there.  Trying to use the open end of an end wrench is just  
> as problematic as the angle from which you can get at the bolt  
> positions the wrench in a manner that as you turn it, the outside of  
> the wrench hits the flange going to the manifold from the turbo.   
> What I figured out was using a crows foot, I was then able to put a  
> 19mm open end wrench on the drive portion of the crows foot, and  
> loosen the bolt with the wrench jutting from between the main  
> downpipe run and upper flex-coupling attaching to the waste gate.   
> Between that combo and a bike cone wrench, I finally worked the bolt  
> loose.
> 
> This brought on the second problem.  As you back off that nut, it  
> runs into hot side turbo housing.  That's when I figured out the flex- 
> coupling had to be removed from the downpipe at it's "down-stream"  
> side to allow enough movement in the exhaust to get that bolt off the  
> stud.  Of course, before getting into all of this, removing the  
> airbox and heat shields are paramount.
> 
> So now the car is running, the turbo is back on and I've got a head  
> full of more Audi 200 related mechanical trivia.  Did this work in  
> solving my problem?
> 
> To recap, the problem is/was excessive oil consumption (1qt/500- 
> miles); smoke on startup; and billowing clouds of oil smoke upon  
> starting to move after idling for more than about 15-minutes. The two  
> competing theories were valve stem seals or turbo seals.  I started  
> with the turbo after inspecting the intake path, finding quite a bit  
> of oil in the hose between the turbo and the intercooler, the  
> intercooler, and the michelin man hose; noticing free-play in the  
> turbo shaft; and finding the car didn't smoke on startup after  
> cleaning these pathways of oil.  After getting a new car, I also  
> found the 200 would still smoke on startup after sitting for several  
> weeks.  Thinking on this second data point was in that period of time  
> (1-2 weeks), given that the engine is not vertical, oil that seeped  
> past the stem seals would have had ample opportunity to go right past  
> the pistons and rings into the crankcase.  It all seemed logical.
> 
> That said I began to have doubts when I noticed the replacement turbo  
> I'd received, one removed after 90k miles, had about the same  
> freeplay in the turbine shaft as my turbo...but felt a little more  
> confident when I noticed upon removal of the old turbo there was oil  
> on the coldside turbo output path, but on the intake side of the  
> intake impellers.
> 
> Back to the "did it work" question.  So far I'd say no, as the other  
> day on my first trip with the new turbo got that same smoking after  
> idling condition.  Ironically, this smoking happened after sitting,  
> and waiting for my chance to take an emissions test.  Car passed with  
> flying colors, then as soon as I pull off that lot notice the  
> familiar haze.  Luckily for me, I found enough humor in that irony to  
> avoid the frustration the continuing problem presents.  On the bright  
> side, for some reason oil pressure has gone down since installing the  
> new turbo, and the new turbo seems to spool up faster.  The first I  
> can objectively measure, the second may just be me justifying.
> 
> While it's possible some oil was getting past the seals in the old  
> turbo, and I will see overall consumption drop, the main thing I was  
> trying to alleviate in this endeavor (billowing after idling) has not  
> been solved.  As of yet, haven't driven enough miles to see where  
> consumption is at.
> 
> My new working theory; must be the stem seals/the head.  Perhaps  
> while idling for long periods of time, the oil that does get past the  
> stem seals winds up accumulate in the cylinder during this high- 
> vacuum/low turbulence state.  Step on the gas, turbulence goes up to  
> level sufficient to make the accumulated oil airborne, and I get to  
> play James Bond during rush hour traffic.
> 
> Hopefully, this information will at least prove beneficial to others  
> down the road, and feel free to interject with theories as seen fit.
> 
> Derek P
> 
> 
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