[2..7t] hunting for boost leaks?

[Jim Green]

On Tue, 9 Nov 2004 22:19:32 -0500, David Kavanagh <audiguy at gmail.com> wrote:
> I was measuring block 115 which shows expected boost and actual boost
> as the car is running. From what I can tell, the actual values are a
> bit off from the expected values when the engine is under load. So, I
> went on a hunt for a boost leak (I should also mention, I've been
> monitoring a MAF with low output for many months now).
> I tested the bypass valves. They both hold a vacuum and the diaphram
> moves predictably as I apply a vacuum. I checked that hose that
> connects the 2 pipes to the throttle body. I felt around after
> unhooking those 2 pipes and can't feel any rips or tears. The hoses
> that connect to the bypass valves seem intact also. Are there any
> others I should have been worrying about? Anything else that might
> cause low boost?
> Bear in mind, I don't know if the boost is all that much lower than it
> should be. I might also be seeing lower boost because the MAF output
> is lower than the computer can adjust for (via fuel trim). It still
> isn't throwing certain codes that will cause Audi to replace it under
> warranty (which is my goal instead of shelling out $250 for a new one
> myself).
> Anyway, any other trouble areas with respect to boost leaks on these engines?

The best way to really test for boost leaks is to pressurize the whole
system.  This might be a royal PITA on your car, but pull the turbo
outlet hoses off, plug them with whatever you can find at Home Depot. 
Find a port or T into a boost line that will fill the entire intake
with compressed air.  15-20 psi will usually tell all.
-- 
Jim Green
'89 90tq
'89 80q
http://www.mswanson.com/~jgreen/car_home.html