Re: Brake adjustment

[Jad.Duncan@GAT.COM (Jad Duncan)]

First, I just re-read my E-mail and must apologize for the typos, 
particularly the Quattra/Quattro error.  Really dumb, I am new to the list, 
but have enough of a brain to spell my cars name, I promise.  It was 
suggested my brake actuation problem might be caused by the hydaulic booster 
and pressure accumulator, however, from looking at the system, I believe the 
90q has a vacuum brake boost.  I am guessing this because there is a large 
vacuum? hose between the black plastic booster part of the master cylinder 
and the fuel injection throttle body.  

I am going to try yet again to adjust the brake pedal rod after work today.  
The brakes, and I believe the rod, were adjusted just before I bought the 
car and it has always had the problem. I am assuming, maybe incorrectly, 
that the car has not done this for its entire 7 year life. Previously, I was 
not able to tell if the nut was part of the clevis/U-bolt or not.  Guessed 
wrong of course.  I will try to break it loose and see if that works.  In 
the unlikely I still can't adjust the rod, I may try blocking the vacuum and 
drive very carefully without the brake booster in hopes of isolating this 
problem.

A couple of people suggested the pedal was catching or blocked, but the 
problem only occurs when the brakes are not used.  In addition, the cruise 
works fine and the brake lights do not remain on.  I am still open to any 
other possible suggestions.

Thanks

>Jad Duncan wrote:
>> 
>> I have an '89 90 Quattro that is a great car exept for a wierd brake
>> problem.  After driving the car for about 10 miles on the freeway without
>> using the brakes, they begin to apply themselves.  The pedal becomes rock
>> hard, does not move and all four wheels seems to start dragging evenly.  A
>> hard jab of the pedal releases everything and the car is fine.  The ABS
>> switch has no effect on the problem and the brake system checks out fine by
>> the dealer and an Audi specialist.  I believe, though grasping a bit, that
>> the pedal is simply adjusted to high.  There is virtually no play, which is
>> usually great, but as the fluid warms and expands I think it needs just a
>> little more room.  The pedal has a threaded adjuster, but I have been unable
>> to adjust it.  I can remove the U-joint from the brake pedal, but as I turn
>> the adjust nut, the threaded rod turns as well.  I have tried to lock the
>> rod with vice-grips, but access is limited and it still spins.  Is there
>> something I am missing in trying to adjust this?  I am geeting really
>> frustrated, but don't want to spend another $100 at the dealer to here the
>> brakes seem fine.
>> 
>> Thanks for any advice.

>Jad:
>Interesting problem. If your car has hydraulic booster and pressure 
accumulator(driven 
>by Hydraulic pump), I would suspect the the brake booster or  the master 
cylinder. Some 
>pressure may be reaching the booster or master cylinder and applying the 
brakes. Kicking 
>the pedal may help close the valve or (as you say)someone adjusted the 
pedal pushrod too 
>long. The pushrod has a threaded end, a locking nut and a clevis. You must  
loosen the 
>locking nut before you attempt to turn the pushrod. Use a wrench on the nut 
and another 
>on the clevis. I don't believe the pushrod length is your problem. Did 
anybody reset the 
>length ?. I am more inclined to suspect a hydraulic pressure issue, if your 
car has the 
>system.
>Good luck
>Pablo
>
>
>
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