ABS problem
Moderators:davidr, BigCatXJS, dhdove
I have a 1990 3.6 auto coupe - a couple of months ago it went in to Jag independent for rear brake disks, pads and h/brake pads (not much change out of 600 quid !). When I picked it up there was a problem that wasn't there before. When braking, just before coming to a halt, the ABS starts chattering away. It doesn't matter whether braking from high or low speed it always kicks in just before coming to a stop. It sometimes carries on when actually stopped and the brake pedal has been released. It doesn't seem to affect the braking efficiency but can be very annoying. I had it back to the garage and they had 4 hours on it (while I was waiting) but to no avail. Any ideas anyone ?
A couple of thoughts;
1. Does the yellow abs warning lamp light illuminate when the ignition is first turned on, and goes out when the pump stops. ie fluid pressure and warning lamp working correctly.
2. Do the warning lights (yellow or red) come on at any other time when driving or braking indicating an actual abs fault. If not, could the vibration/pulsing you are feeling be chatter from the new brake discs, exhaust, prop shaft or hydraulic accumulator pump.
The abs system is disabled below a certain speed, I think its 5mph, so if the problem is with the abs I would be looking carefully at the rear wheel sensors or wiring, although if that was the case you should get a yellow warning light.
Pop
1. Does the yellow abs warning lamp light illuminate when the ignition is first turned on, and goes out when the pump stops. ie fluid pressure and warning lamp working correctly.
2. Do the warning lights (yellow or red) come on at any other time when driving or braking indicating an actual abs fault. If not, could the vibration/pulsing you are feeling be chatter from the new brake discs, exhaust, prop shaft or hydraulic accumulator pump.
The abs system is disabled below a certain speed, I think its 5mph, so if the problem is with the abs I would be looking carefully at the rear wheel sensors or wiring, although if that was the case you should get a yellow warning light.
Pop
Hi guys and thanks for your feedback. Many apologies for the delay in replying but I don't drive the car every day and I have been trying to pay more attention to the problem in light of your comments. My recent observations:
1. The yellow abs warning light comes on at start-up then goes out after a few seconds.
2. Yellow or red warning lights do not come on at any other times.
3. Can't be from the new disks as the chatter is at a constant speed irrespective of vehicle speed and can carry on briefly after vehicle stopped.
4. Pulsing thro' brake pedal therefore not exhaust problem.
5. Don't think it is the prop shaft as can occur when stationary.
6. Pop, not sure if I could tell if it was the hydraulic accumulator pump.
7. When you mention the speed thing, it is definitely kicking in below 5 mph, almost at a standstill.
Not being of a mechanical nature, could any crud be cleaned off the sensors with a well aimed hose (at mains pressure of course) or is this a stupid question ? One final thing, I decided to check the brake fluid level (which I wouldn't expect to do having spent all that money !). The level was way over ! I primed the system correctly as per the handbook before checking. I then managed to remove 2/3 of a pint to reduce it to the max level. Could this have damaged the system in any way ? There must be a reason for a max level.
Thanks again,
Pete
1. The yellow abs warning light comes on at start-up then goes out after a few seconds.
2. Yellow or red warning lights do not come on at any other times.
3. Can't be from the new disks as the chatter is at a constant speed irrespective of vehicle speed and can carry on briefly after vehicle stopped.
4. Pulsing thro' brake pedal therefore not exhaust problem.
5. Don't think it is the prop shaft as can occur when stationary.
6. Pop, not sure if I could tell if it was the hydraulic accumulator pump.
7. When you mention the speed thing, it is definitely kicking in below 5 mph, almost at a standstill.
Not being of a mechanical nature, could any crud be cleaned off the sensors with a well aimed hose (at mains pressure of course) or is this a stupid question ? One final thing, I decided to check the brake fluid level (which I wouldn't expect to do having spent all that money !). The level was way over ! I primed the system correctly as per the handbook before checking. I then managed to remove 2/3 of a pint to reduce it to the max level. Could this have damaged the system in any way ? There must be a reason for a max level.
Thanks again,
Pete
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