R.E. ABS with a bad case of timing

[Simon Allcorn <SALLCORN@softa.co.uk>]

>Erratically but while coasting to a stop, the sound of the ABS on my 1988
>90Q kicks in from say, 5 mph down to 0 mph. The noise that I'm hearing and
>the pulse that I am feeling through the brakes is the last part of the
>normal ABS action when coming to a stop. This noise completely excludes >the
>first part of ABS where one hears the rapid clicking sounds as the car
>would rapidly decelerate.

This is exactly what the ABS does on my 87 coupe Quattro. I have been
told by a friend who is a car designer that this type of bosch ABS has a
speed senser that turns the ABS off if the car is travelling below 5
MPHish. I have also found that going along at some speeds (say about
2MPH) with my foot lighly on the brake I can get the ABS to trigger all
the time. I have no idea where or what form this ABS speed sensors takes
but if you do find out, let me know. Cheers.


>The ABS braking action is normal when panic stopping from 50 mph speeds >o
> mph. The ABS is always on but this groaning occurs whether the ABS is on
>or off.

The groaning could be the ABS system evacuating after an actuator has
fired or the system has a leak - this is only a guess though - does
anybody else have any ideas ?