Date:         Thu, 16 May 2002 13:58:45 -0400
Reply-To:     "G. Matthew Bulley" <gmbulley@BULLEY-HEWLETT.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         "G. Matthew Bulley" <gmbulley@BULLEY-HEWLETT.COM>
Organization: Bulley-Hewlett
Subject:      Re: disc brake pressure regulator
In-Reply-To:  <Pine.GHP.4.30.0205160837270.29256-100000@raptor.csrv.uidaho.edu>
Content-Type: text/plain; charset="us-ascii"

Flat out: the problem ISN'T the regulator.

The regulator relies on inertia (forward movement of the van) to
function. There is a little "ramp" inside it, and a heavy "ball"... the
harder/faster you brake, the further up the ramp the ball rolls, sending
more hydraulic pressure to the front the farther up the ramp the ball
rolls. Make sense? Even a complete failure of this system (never heard
this happening) wouldn't lead to the problem you have.

Okay, back to your problem.

You futzed something up in the brake booster vacuum system. You have
something bassackwards or something. I've never seen such as you
describe, but based on the symptoms, the diaphragm is pushing against
the master-cylinder pushrod ever so slightly. What happens if you start
the engine and apply the brakes? Do all of the wheels stop/hold
normally? What if you pump the brakes 5-10 times in rapid succession
with the motor idling (bleeding out all the vacuum). Will the front
brakes free up?

Either way, I think rechecking your prior work would be my first step.
Next I'd look at the booster, then the Master Zylinder.

Pax--

G. Matthew Bulley
Mount Olive, NC


-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf
Of David White
Sent: Thursday, May 16, 2002 11:57 AM
To: vanagon@GERRY.VANAGON.COM
Subject: disc brake pressure regulator

Who has experience with the pressure regulator for disc brakes on the
air
cooled vanagons? I have a 1981 vanagon with an interesting problem.  As
soon as I start the engine the front wheels pretty much lock up--I
cannot
turn the wheels by hand and the van feels very underpowered. The rear
wheels spin fine. If I turn the engine off for about 15 minutes the
front
wheels loosen up and will spin. I have loosened the brake line at both
front wheels and there isn't alot of pressure in the line.

The only other clue I will give you is that I recently replaced some of
the elbows and vacuum hoses that go to the brake booster.

After looking through the vanagon manual I see that there is a regulator
for the disc brakes.  My original plan was to replace the master
cylinder
but now I wonder if the problem is in this regulator and not the master
cylinder.

My main question is whether there is a way to test the regulator and/or
the master cylinder while they are in the vehicle so that I don't have
to
replace both. For example if the master cylinder is not releasing
correctly will there be high pressure in the brake line that leads to
this
disc regulator whereas if the problem is the disc regulator then will
the high pressure be in line after the regulator?

Finally the idiot's guide firmly states that backyard mechanics such as
myself shouldn't even mess around with this disc pressure regulator and
instead put this repair job into the hands of a qualified mechanic. I
understand the function of this regulator and it seems like I'll know
pretty quickly if I did the job right--the rear end will lock up when I
apply too much pressure to the brake pedal. Am I close? I live out in
the
sticks so I can take a test drive without the worry of harming others.
The worst thing that could happen is that I end up in the ditch.

Thanks in advance,
David