[Biturbos4] boost leak?

David Kavanagh audiguy at gmail.com
Mon Nov 8 22:37:58 EST 2004

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 boos 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
Anyway, any other trouble areas with respect to boost leaks on these engines?


'00 A6 biturbo 6-speed
'01 allroad 6-speed

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