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