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5000s brake woes

>From: Alexander van Gerbig <avangerb@zoo.uvm.edu>
>Subject: 5000s brake woes
>My sister owns an '86 5000s Automatic.  The car has a funny problem that
>I have never heard of before.  She was driving down the highway and
>hadn't touched brake pedal for quite sometime, when she did go for the
>brakes the pedal was rock solid giving only about an inch of travel then
>going hard.  After noticing this she released the pedal and began to
>notice that the car began to slow on it's own.  The car's brakes were
>grabbing more and more by the second.  She accelerated and the car still
>became slower.  The steering wheel began to shake, so she pulled off to
>the side of the road.  Slowly but surely the brakes let up and she was
>on her way, although it took some time.  This brake seizing had occurred
>before in stop and go traffic.  After a couple minutes of driving or
>waiting will fix the problem.  Any ideas guys?  Maybe the accumulator?
>Brake fluid is still amber, not dark.  Has new bleeder nipples in the
>rears, new flex hoses all around, and new rotors+pads in the front.
>Thank you,
>Alexander van Gerbig '88 80

First stop is change the master cylinder. Non-releasing brakes on type 44
cars are almost always caused by this. You can buy a rebuilt master
cylinder at Discount Auto Parts, Pep Boys, AutoZone, etc. for MUCH less
than at Audi - I think about $40! - and they work just fine. Don't try to
rebuild your old one - parts are often not available. Make sure you use
DOT-4 brake fluid - cheaper DOT-3 attacks the seals. If you pre-fill the
new master cylinder completely and carefully, and don't disturb the brake
lines coming from it too much, you'll have enough brakes to get it
someplace to be bled. Standard procedure, but there's a proportioning valve
inboard of the left rear wheel which is sometimes a little stubborn about
bleeding completely.

After the master is changed, then do the bomb check. Run engine, turn it
off, pump brake pedal. You should get 15-20 pumps before the brake pedal
gets "hard" - this is a very distinctive feeling - you will be able to tell
it is different from the feel of normal brakes. If the pedal is hard and
"pulsates" with the engine running, the bomb is DEAD.

Many people continue to drive type 44 cars with dead bombs - the difference
is HUGE - and having experienced before and after, I WILL NOT EVER AGAIN
drive a type 44 with a dead bomb - it isn't safe! With a dead bomb, the
brakes are just barely adequate for normal driving, and will give the
impression that they are fine - they are NOT, and there is NO reserve for
emergency stops. With a new bomb, the brakes are FABULOUS!

Bombs cost $225-$250 or so, and there's a lister in Colorado who is
recharging them for $50 - no personal experience.

Best Regards,

Mike (let there be Euro-lights!) Arman