[urq] an ABS issue?

[Tony Hoffman]

That car uses a hydraulic assist for the brakes. It sounds like you might have a problem there. I'd check for leaks, but you might also have an internal pressure problem. Perhaps a bad pump or blockage in one of the lines. 
 
To check for the problem to be assist related, get the car up to speed on a deserted road. Then, turn it off - remembering you will also loose power assist for the steering - and push on the brakes. If the pulsing is gone, it is an assist problem.
 
Also, does it do it while stopped as well?
 
Tony Hoffman

"spot.ontheroad" <spot.ontheroad at virgin.net> wrote:
Starting a new trend , I'm the first to reply to my own email.
Well, I removed the ABS fuse, the ABS warning light came on as expected to
show that the system is not functioning and the problem remains. The pedal
still pulses under braking. So I guess this rules out the ABS as the cause.
Am I being thick here and have overlooked something ridiculously simple?

Keith



----- Original Message ----- 
From: "spot.ontheroad" 
To: 
Sent: Sunday, August 07, 2005 6:15 PM
Subject: [urq] an ABS issue?


> Afternoon/evening all. My apologies for the non-urq content but it is an
> Audi problem.
> My good lady's 1993 Audi 100 Avant has a braking issue which I am trying
> to solve. The problem is constant pulsing through the brake pedal whenever
> the pedal is applied - just as if the ABS is engaging all the time. My
> immediate thought was warped discs (rotors) so I bought some new ones. The
> old ones were less than 1 year old and I presumed they must have been
> inferior quality and had warped. Anyway the new (brembo) discs have made
> no difference at all. There is still a constantly pulsing pedal.
> My thoughts are now that it is an ABS issue not a disc problem. There is
> no provision on this car to turn off the ABS as far as I know.
> I intend to remove the fuse that handles the ABS and see if the pulsing
> goes away.
> If it does - it points to it being an ABS problem for sure, but what do I
> then check and how?
> If I pull each wheel sensor out one at a time, is it possible to tell
> whether or not it is functioning perhaps by testing resistance?
> Can a wheel bearing problem cause this. We have the beginnings of a wheel
> bearing whine but I can't tell which front wheel it is. There does not
> seem to be any wheel bearing "play" yet in either wheel.
> Any suggestions of diagnosis methodology and possible fix will be greatly
> appreciated.
>
> Many thanks
>
>
> Keith
>
> '87 WR
>
>
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>


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