Changing Turbo...what I've learned

[Derek Pulvino]

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