200 TQ Hissssssssss....

[Kurt Wesseling]

Guys:

Remember me?  8-]  Been lurking for the past 8 months or so.

Patient is my 89 200 TQ with 193,000 miles on the clock, 1.8 bar WG spring, no chip.

Last week I noticed a loud hiss from under the hood at 1.0 bar and above.  The higher the boost, the louder the hissing. Thinking it was something in the turbo circuit, I took it in to my mech for a look.  We found several broken EM studs and that the EM was cracked.  Not really any surprises there.  Seemed reasonable to think that would cause the hissing.  I had him replace the studs and weld up the cracks since a new manifold is around $900.00 USD. Picked the car up yesterday and it is still hissing.  The $720.00 EM repair changed nothing--made the car a bit quieter, I suppose.

Symptoms are similar to those many of us have seen with a split IC hose--except the hose is ok.  If I keep pushing beyond 1.1 bar, I get black smoke from the exhaust and the engine begins to stumble.  Sparks plugs, W7DTC's, show no significant oily deposits and are light gray at the electrodes. When I let off the accelerator the hiss continues for about two seconds and slowly dies off, leading me to believe that some component is being pressurized and the air is escaping from a small hole somewhere.  

So what do you think--small hole in the intercooler?  The ends don't appear to be loose.  Perforated WG diaphragm? Some gasket I don't know about?  

Opinions very welcome!

Thanks,

--Kurt

1989 Audio 200 TQ, 1.8 bar ...usually!
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