> there's only so much vacuum volume in your reservoir.  You should only
> get one or two soft brake applications with the engine stopped before
> the reservoir runs out.  It's just an emergency thing so that if your
> engine stops while you're driving, you can safely stop the vehicle.
> 
> As for the sound, is it not just the normal power assist hiss?

Hi.  Thanks for your reply to my puzzle.  The vacuum hiss is ever 
present when the brakes are applied as of late.  Never heard it 
before.  Had the car since new (1988).  Instead of a sudden vacuum 
hiss upon applications, it keeps hissing as long as the brake is 
applied.   It sounds like the vacuum can't keep up with the draw from
the power booster.   With the engine off, and with the pedal depressed
and held, you can hear the vacuum bleed off, and the pedal goes
"hard"... meaning you need mega force to apply the brakes as there is
no boost.  I suspect the vacuum is totally depleted, whereas, as you
say, you should get a couple applications before this happens.  I guess
what I am trying to say is that vacuum is not being held in the power
booster.  All lines look good (no chaffing or cracked lines), and
connections look solid.  

I'm not sure if this is a safety issue or not as the pedal feels fine
as long as the engine is running.  Do you think this can wait until a 
more convenient time?

Thanks again for your time.

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