ABS fault

[guitarfish]

I have an ABS light come up while driving. The ABS hydraulic control unit whines for up to an hour after the vehicle is turned off. ABS doesn't work - the wheels lock up when I slam on the brakes. The car is a 1990 525i e34. Where should I start looking?

[shogun]

see my website below under
Any other problems ? Have a look at this site : http://www.bba-reman.com/bmwabsfaults.htm

it is almost at the bottom of the page

[guitarfish]

Thanks Shogun - There is some good stuff in there.

I was thinking about what caused the "fault" and penny dropped. It occurs every time after a Warrant of Fitness (this is a NZ Govt check to make sure your vehicle is roadworthy). Part of this check is to test the effectivness of the brakes so I guess they apply the brakes hard (activating ABS). The ABS light no longer came on and the HCU wasn't running after a couple of days so I took the car for a run and the ABS worked (followed by another HCU whining). After another couple of days the ABS system was OK.

Is this normal operation after activating ABS?
What is the HCU trying to pressurise?
If it is not normal, what can I look at to fix it?

[guitarfish]

Couldn't find a fix on Shoguns webpage. This problem now occurs intermittantly and runs my battery down. Does anyone know how to disconnect the ABS system? I can live without it.