Faulty Proportioning Valve ?

[Fred Munro]

I don't know if the '90 uses the same lever-actuated rear proportioning
valve used on the Type 44 (a spring attached to the rear control arm moves a
lever on the proportioning valve which adjusts the valve position for load),
but if it does, they seize up in rust belt application. To check it, try to
move the lever by hand. If it doesn't move, valve is pooched. If it does
move, put your hand on the lever and have someone apply and release the
brakes. The lever should "kick". If it doesn't the valve is pooched.

The only source for replacements is the dealer for mega $$$.

HTH

Fred Munro
'94 S4


-----Original Message-----
From: quattro-bounces at audifans.com
[mailto:quattro-bounces at audifans.com]On Behalf Of Greville Bowles
Sent: November 12, 2004 4:50 PM
To: Quattro List
Subject: Faulty Proportioning Valve ?



Well, we have started to narrow down the possibilities re: the rear rotor
corrosion problem on my '95 90Q. First some background:

New rotors & pads all round - Fall 2002

Replaced rear wheel bearings - Summer 2003. There was no apparent brake
problem at that time.

Oct. 2004 - replaced very noisy right rear wheel bearing. Left side is ok.
During that work it was apparent that there was a problem with the rear
brakes, in that the rotors we very corroded and making minimal contact with
the pads.

Last weekend - Replaced rear rotors, cleaned and inspected calipers,
replaced rubber booties. Observations:  Pads only lightly worn. While
tightening the wheel bolts the real wheels could be turned by hand with the
brakes applied (read: 0 stopping ability) The hand brake functioned fully,
solidly locking the wheels. The front brakes are working well.

So, I'm thinking it's time to look at the hydraulics, and my first guess is
a faulty proportioning valve. Bentley tells me to use the VW1310 tool (a
pair of hydraulic gauges on a stand) to simultaneously measure the pressure
at the left front & left rear bleeder valve. If the pressure is outside the
given range, replace the proportioning valve. Since I don't have the VW1310
tool, this sounds like a dealer visit.

Before I go to the dealer, is there anything else I should look at that will
help to diagnose the problem? Any BTDT's?

The following is more background just in case there is some relationship
that I'm not seeing. It may mean something to others.

Once I get the brake issue(s) resolved I'll need to find out why that rear
bearing went so quickly (24,000 miles). The noise started during a trip to
NC. I had the alignment done down there and the mechanic said that the rear
wheels were way out of alignment. Alignment was done less that 1 year prior
and I've had no "incidents" since then. I assume that was the cause of the
odd wear pattern on my new tires (1-2 inch wide bald strip on the inside
edge of the rear tires).

Another item I need to look at is amount of play in the drive train to the
rear wheels. I can turn the wheels 3 to 4 inches with little or no
resistance. Is this normal? Perhaps the CV joints are worn? Or the
differential?

The clutch release bearing is getting rather loud. I suspect that will need
attention soon. What all should be done "while we're in there"?

Every time I do something on this car I'm into the great unknown. If not for
the helpful folks on this list and my good buddy George, I'd be spending a
fortune at the dealer (or driving a Kia). Thank you 1 and all for keeping my
sorry ass out of a Korean tin can.

****************************
I just called the dealer.

Clutch job (disk, pressure plate & bearing) = $1100 + tax
Proportioning valve $200 + $126 labor + tax

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Mr. Greville H. Bowles
RR 5, Rockwood, Ontario N0B 2K0
E-mail:   zaphod at cansafe.com
'95 90Q
'85 245
'83 GS650GL
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~



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