Hi Everyone.  This isn't related to my van, but my diesel Golf.  I 
suppose the same symtom could occur in any vehicle that uses power 
brakes, and may be relevant here.

Upon brake pedal application, there is what sounds like a vacuum leak 
coming from the power brake booster unit in the engine compartment, 
but very hard to pinpoint.  It is really noticable with the engine off, 
and then press on the pedal.  The air in the booster is released, and 
the pedal effort is very hard to apply the brakes (no more boost).  I 
have a Bentley manual for this vehicle, and it mentions that there is 
a check valve in the vacuum hose that holds vacuum in the booster 
when the engine is stopped.  It doesn't say where it is located in 
the vacuum line, nor how to change it.  Bentley doesn't even show 
what it looks like.   Brake pedal feel, and brake performance is
excellent with this exception. 

The vacuum lines look good, and the vacuum pump is working quite 
well. 

 Ideas?  I was thinking of taking it to the shop to fix, but would 
appreciate some of the lists valued opinions before doing so.

Thanks in advance.

Cheers,
Harry.

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Harry Yates      Internet: hyates@bcit.bc.ca
'90 Syncro Westfalia
'87 Golf Diesel