850R (96) Brakes

Hi, driving to work today I heard a sort of humming sound from the front of my 96' 850R which lasted for about 2 minutes and the brake pedal went very hard (though it still worked) as though it had no power assist at all. As luck would have it I was 1 block away from my mechanic so I left it out the front. I haven't heard from him yet but I'm curious as to what may be the problem (and more so the likely damage$). I only had the brakes overhauled about 5 months ago.
Regards Luke

[noiseboy]

Did the hum change pitch with speed???

In that case (and considering the pedal feel) it could be a seazed caliper - which is about £150 + labour, as memory serves.

Are you in the UK or the US?

Regards,

Phil :-)

[Simon Linton]

I speak from bitter experience to say that a siezed caliper means two front discs as well as the caliper assembly.

This will be more like £250 than £150 - sorry.

I'm in Australia. My mechanic had it for 3 days and couldn't find a thing. Hasn't happened since. The sound seemed to be a constant pitch, though very dull sound. He said the caliper's are OK.

how about an abs computer? Did the car trip a code for that? Any abs /tracs lights?

>how about an abs computer? Did the car trip a code for that?
>Any abs /tracs lights?

The ABS light has been more or less constantly on since I got it a year ago. I was told it is some manufacturing problem with the 850. My mechanic said there were no faults registered on the ABS.

I wouldn't agree that the 850 has a manufacturing problem with the abs. If the light was on constantly in the uk then it wouldn't pass an mot test. I think you have an abs problem which, if the computer has gone a bit mad could give a firm pedal without much braking effort as the abs tried to release and reapply the brakes hundreds of times. You would also probably hear a noise from the abs as it did this. If no fault codes are stored, try cleaning the sensors on the brakes and make sure all the wiring is intact.

If it was the ABS wouldn't you get the banging noise, and the banging on the brake peddle as the ABS did it's thing?

Stu

You don't have to get the banging noise, it depends how confused it is, and since his abs light is on anyway it would be a good place to start.

[Mike Arnold]

Ok, I am a trespasser on the 850 site and this is a longshot but here goes...

I used to have a 760 and one day it started buzzing as I pulled away after starting, then the buzz would stop and the ABS light would come on. Upon careful investigation I discovered that a front wheel ABS sensor cable had been half cut through by rubbing against the wheel rim. The cable was shorting which sent the ABS control unit into spasm (buzzing the ABS pump) before shutting itself down when it realised that something was wrong.

Summary: test the ABS sensors.