Date:         Mon, 29 Apr 1996 15:32:01 GMT
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         vw@gulbransen.com (Vw)
Subject:      Re: HIGH BRAKE PEDAL EFFORT ('71 CAMPER)


> this baby down!  I though the front or rear circuit was leaking but 
> front and back wheels bind when I raise the car and have someone push 
> on the brake pedal.  I suspect it might be the assist diagphragm (or 
> whatever you call it) on the master cylinder.  Does anyone know how 
> to diagnose a failure of this unit, or have any other suggestions.
> 

Chris,

First check the vacuum line. It's a large hose going from the assist 
servo, that you identified,  to a connenction to the intake manifold
just below the carburetor.  There is a one-way valve in the hose
where it passes the ignition coil. If the valve is plugged or
installed backwards, the symptom will be difficult braking (brakes
work but you have to press hard).  Part of this vacuum line is a
metal tube. Make sure that the entire line is free from blockage.

After you free the blockage in the vacuum line, you can diagnose the
servo (the large roundish thing to which the master cylinder is
attached). If your servo is bad, when you press the brake pedal the
engine will die because of the massive vacuum leak inside the servo.
The servo cannot be repaired. So, call around and try to find a new
one for under $200 (cheaper at a wrecking yard, but not guaranteed).

BTW, it is important that the vacuum line be routed upwards as it
leaves the intake manifold. Even with the one-way valve in place, the
hose needs to be routed upwards to keep the gasoline (condensed
vapor) from flowing into the hose.  If the servo fills with gasoline,
it will fail quickly because the gasoline will eat the diaphragm.
Happened to me once.

Good luck.
Bob and Penny Lee   vw@gulbransen.com   San Diego, CA
'71 VW Bus White/Blue with sunroof '72 VW Super Beetle White Herbie          
'71 VW Bus Dark Blue with sunroof  '72 VW Super Beetle Orange with sunroof

ÿ