ABS problems

I'm having problems with the ABS on my 940. The brake pedal sometimes pulses when pressed. The ABS sensors have all been replaced as have the rear discs and the front ones have been cleaned and checked. The pump (?) makes a rather disconcerting whirring sound sometimes when I slow down and also there is (occasionally) a nasty graunching sound coming from what feels like the front wheels. Anyone out there got any suggestions?
Nancy

Pulsing at a guess isn't good although it means the ABS is working, ok a little hard (I felt the brake pulse on my Range Rover on hard brake none of the other cars ever have though) The noises could be down the brake pads or fitting kits moving in the caliper.

You could have something contacting either the inside of the hub between the ABS sensor and hub. Are you getting the warning lights on at all?

As for the pump making noises not sure what that can be. You could have an air lock somewhere in the system. I've read that the ABS pumps are fairly common to contain air when the system is bled although this air never gets to the main brake system.

If all is working i wouldn't be worried and as long as the man from the ministry is happy with it's brake efficiency then i'd leave well alone

[adamsky01]

Originally Posted by nancy

I'm having problems with the ABS on my 940. The brake pedal sometimes pulses when pressed. The ABS sensors have all been replaced as have the rear discs and the front ones have been cleaned and checked. The pump (?) makes a rather disconcerting whirring sound sometimes when I slow down and also there is (occasionally) a nasty graunching sound coming from what feels like the front wheels. Anyone out there got any suggestions?
Nancy

ill tell u what is causing it right now and its nothing to bad or costly

ok right basicaly its kind of a warning first hint
that u need to be aware of if u have never done this ur self then go to some wer like kwick fit ask them for a compleate brake fluid drain
or if u are doing it ur self take the cap of smell the new oil and smell the old oil the oil in the car iis probaly going to smell burnt .


how to diy
buy a presure bleder than runs of ur spare tyre
buy a galon of dot 4 brake fluid
then look in ur hains manual for the corect bleding route ie on my its the rear pasenger side first then then driverside rear then the front pasenger side then front driver side ull probaly have to do this abought 5 times to get all the old fluid out
a little tip buy a can of brake cleaner the spay type if u spill any dot 4 on the paint work spray it then mop it up other wise ull lose paint

hope this helps
mike

I had exactly the same problem on my Galaxy. On the Galaxy, the reluctor rings (the things that the ABS sensor reads) are heat shrunk onto the front CV joints. Over a period of time rust gets in and starts to strip off teeth. The net result is when you brake, the ABS sees (actually doesn't see) the missing teeth, and assumes the wheel has locked. Hence it pulses the brakes, exactly as if the system was working fine. You get no fault codes whatsoever, as the system is working fine. I also got the whirring sound you mention, which was the ABS pump working to rebuild the system pressure. I also found that the pulsing stopped at about 5 or 6 mph, which is the speed below which the ABS won't work ( or you could never actually stop the car).
This was costly on the Galaxy, as it needed two cv joints, but the Volvo is of course rear wheel drive, so it may not be so pricy, if that is indeed the problem.
Best of luck.
Dave