PS pump cyl head leaks

Bernie Benz b.benz at
Wed Dec 5 07:05:10 PST 2007


I had a very slow, almost nil leak on the upper PB cyl head on my  
90Q-20V for years. Replaced the O-ring, still leaked. So I really dug  
into the problem.
Problem is that Audi/ZF as well as I had been sizing the O-ring to  
fit the OD of the cyl head. Not correct, as when under pressure, this  
O-ring is forced out against the ID of the housing bore. So, O-ring  
should be a static snug fit against the housing. One size up in OD  
from my standing recommendation is correct. No more weaping leak.
Further, don’t forget that the O-ring must be well greased when  
installing to prevent localized necking down of the O-ring material  
when screwing in the cyl head. Head needn’t be very tight, screw  
driver tight is OK.

On Dec 4, 2007, at 5:54 PM, Dave Defferding wrote:
I will clean and check the car often to find where it's coming from.   
slow leak now, as don't see the reservoir dropping.

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