I'd check the o-ring that's between the master cylinder and booster.
I'd also look for signs of brake fluid inside the booster,
and deteriorated paint on it......from brake fluid leaking from the master
cylinder.

it's odd............great breaking when it's making the sound.
My attention is sure drawn to the booster.
and the vacuum nose from engine to brake booster.

I have seen twice............what looked like to be an ice pick  hole poked
into a vanagon plastic line.......
for no reason 'at all'..............just a hole in the plastic line,
appearing to be punctured in from the outside.

One was a vacuum brake booster line.
one was a plastic coolant bleed rail around the top of a 2.1 waterboxer
engine compartment. And no explanation of how those holes got there at all.

thanks for saying it's a Westy Syncro .  Will be interested to see what you
find.
Scott
www.turbovans.com

----- Original Message -----
From: "Kim Brennan" <kimbrennan@MAC.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Friday, July 31, 2009 2:43 PM
Subject: Brakes, reprise

> Welp, I had hopes that the issue with my brakes on my Westy Syncro was
> the master cylinder. But no such luck. Problem still exists. A review,
> when braking, if I pump the brakes, I'll get braking, but usually all
> the way down at the floor. Occasionally I will hear a airy buzzing
> sound from the center of the dash and on those occasions, I will get
> braking at the top of the pedal.
>
> Since that's come from the center of the dash area, I'll have to
> follow the sound.