If it does turn out to be a faulty brake booster, this would save you about $649.25

http://www.autopartswarehouse.com/details/QQVolkswagenQQVanagonQQCentricQQBrake_BoosterQQ19801991QQCE160-dot-88202.html?apwcid=P1135867996W43b3f85c7ab9e&apwidtZrd3U7

Don
  ----- Original Message ----- 
  From: dvdclarksn@aol.com 
  To: dhundt@bendbroadband.com ; vanagon@GERRY.VANAGON.COM 
  Sent: Tuesday, June 07, 2011 9:15 PM
  Subject: Re: hissing relays?

  Didn't think of that but if I were losing vacuum there wouldn't the pedal be feeling different and coming up (away from the floorboard) more? I will check it though to see if a hose is loose or something else is out of sorts.But no it can't be the booster cause that part is about $750.00 new-yikes!  I'm thinking about an upgrade with it eventually. Seems as though I have read that the E30  or E36 series BMW can be modified to fit a vanagon and provides more assistance to go along with other brake upgrades. I'm the service manager at our local BMW dealership and I know one of my techs has bound to have a good used one for sale. For the life of me I can't figure out why or how a relay could make a hissing sound. I will listen again with my "listening tube" (approx. 18" long piece of automotive hose with about a 1/4" I.D.) before I tear the dash apart. Well going to do that anyway to fix the blankety blank odometer, ribbon cable conn. problem and radio issue. Put it on the Westy project list I guess.

  David Clarkson
  90 westy with a serpent in the dash

  -----Original Message-----
  From: Don Hundt <dhundt@bendbroadband.com>
  To: dvdclarksn <dvdclarksn@AOL.COM>; vanagon <vanagon@GERRY.VANAGON.COM>
  Sent: Tue, Jun 7, 2011 8:04 pm
  Subject: Re: hissing relays?

Your brake booster is in roughly the same location as the relays, that may  
be where your hissing is coming from. 
Don 
----- Original Message -----  
From: "David Clarkson" <dvdclarksn@AOL.COM> 
To: <vanagon@GERRY.VANAGON.COM> 
Sent: Monday, June 06, 2011 9:45 PM 
Subject: hissing relays? 
 
 
I've been listening for something on my vanagon for a while. There is an  
audible hissing noise that seemed to come from one or both of the relays  
used for the very common headlight upgrade. I thought at first that there  
was some sort of grounding problem tied into either the amp, crossovers or  
stereo receiver but recently disproved that when the radio was disconnected  
completely and removed. I have also had pulled the fuse on the amp as well.  
I still had the hissing noise that would continue for about a second after  
the engine was shut off. The noise occurs whether the headlights are on or  
off. My question is could this be a grounding problem with the relays or  
simply one or both of the relays themselves? This is the second pair that I  
have had after one got broken when it came loose in the dash and when a fuse  
for the relay power was damaged it melted down the other. The original pair  
did not cause any hissing but it seems that I changed something like maybe  
the grounding point for the relays. Anyone out there had a similar problem  
or maybe some explanation or fix. I have heard of buzzing relays? before but  
not one that mad a hissing sound like air being let out of a tire. Thanks  
for any insight that anyone can offer. I'm thinking that I might just buy a  
couple more and maybe get a slightly more expensive and hopefully better  
quality relay. With this 21 yr. old van that is approaching 300k on a  
rebuilt engine I really am tuned into any noises especially one that might  
mask a more serious noise. 
 
David Clarkson 
1990 Westy Ssssssss....