tmarshall57
New member
I have just fixed an ABS problem on my daughters car. Here is a description of the fault, the diagnosis and the solution. Hopefully this will help others. I have gone into some detail because some of the descriptions of previous problems/resolutions on this site have been a bit brief.
Background: I replaced the rear brake shoes and drums a few months ago. When refitting the shoes on one side I noticed that that one of the springs on the auto brake shoe adjuster had broken. I checked the price at a fiat dealer and was told the price of a replacement was approx £30. The local scrap dealers didn't have any so I decided to turn the adjuster manually and replace the adjuster later. Wrong decision!
Last week my daughter said that her brakes felt funny as though the ABS was kicking in even at very low speeds. I checked this out and she was right - the ABS was kicking in and it felt like it was happening briefly once per wheel revolution. Once or twice the yellow dash ABS light would come on and stay on. When the car was restarted the ABS light would go out but the problem with the ABS kicking in remained. I disconnected fuse 4 under the bonnet to disable the ABS. I looked on this forum and found that the most likely cause of the problem was:
1) Dirty ABS sensors
2) Bad connections between the sensor wire and the wiring harness
3) Worn wheel bearing causing damage to the magnetic ring on the hub (which sends a signal to the ABS sensors)
4) Other mechanical damage to the magnetic ring on the wheel hubs
I checked the wire connections (white plastic tube like things) on each side of the engine compartment under the bonnet) for the front sensors and these were fine. I tried removing one of the front sensors however these were rusted in and I didn't want to risk breaking them.
Before checking the rear connectors I thought about the situation and decided to check the rear wheel hubs since I had recently replaced the rear brakes.
I removed one of the rear brake drums and immediately saw that there was some mechnical damage to the magnetic ring at the rear of the wheel hub. In fact there was a 1 mm gap at one point on the circumference. This had obviously been the cause of the ABS kicking in as each time the gap in the magnet passed the sensor the ABS unit thought the wheel had locked.
I checked the other wheel and there was no similar damage to the magnetic ring.
I then realised that in order to fix this problem a new hub was required - it was not possible to replace the magnet. I purchased a new hub kit (including new nut) from Partco (Unipart) for £55 inc VAT. I also bought a torque wrench capable of 250 ft lbs of torgue (204 lb/ft required for the hub nut). I bought a pair of rear brake adjusters (as I had noticed the one on the other rear wheel was damaged also) from partsworld-uk.com for £32 or so.
I replaced the hub and adjusters last night and when removing the old hub noticed that there was a much greater amount of damage to the magnetic ring than there had been previously. Be careful when loosening or tightneing the hub nut - a quality wrench and socket are required. When tightening the nut the short socket extension actually twisted and sheared.
Casue of problem: It seems that, if the rear brakes are not adjusted correctly via the auto adjusters then the handbrake mechanism on the rear brake shoes will travel further than intended and eventually scrape against the magnetic ring on the hub - therefore casusing at least £55 of damage in a short space of time as the magentic ring is made of some sort of soft plastic.
After replacing the hub and adjusters it is important to repeatedly depress the brake brake pedal (with the handbrake off) to ensure correct adjustment of the brake shoes - do this at least 30 or 40 times or until you can't hear the click of the auto adjuster.
I've just replaced the fuse and tested the car and everything seems OK.
Sorry for the long post but this might save some of you a lot of messing about.
Tony
Background: I replaced the rear brake shoes and drums a few months ago. When refitting the shoes on one side I noticed that that one of the springs on the auto brake shoe adjuster had broken. I checked the price at a fiat dealer and was told the price of a replacement was approx £30. The local scrap dealers didn't have any so I decided to turn the adjuster manually and replace the adjuster later. Wrong decision!
Last week my daughter said that her brakes felt funny as though the ABS was kicking in even at very low speeds. I checked this out and she was right - the ABS was kicking in and it felt like it was happening briefly once per wheel revolution. Once or twice the yellow dash ABS light would come on and stay on. When the car was restarted the ABS light would go out but the problem with the ABS kicking in remained. I disconnected fuse 4 under the bonnet to disable the ABS. I looked on this forum and found that the most likely cause of the problem was:
1) Dirty ABS sensors
2) Bad connections between the sensor wire and the wiring harness
3) Worn wheel bearing causing damage to the magnetic ring on the hub (which sends a signal to the ABS sensors)
4) Other mechanical damage to the magnetic ring on the wheel hubs
I checked the wire connections (white plastic tube like things) on each side of the engine compartment under the bonnet) for the front sensors and these were fine. I tried removing one of the front sensors however these were rusted in and I didn't want to risk breaking them.
Before checking the rear connectors I thought about the situation and decided to check the rear wheel hubs since I had recently replaced the rear brakes.
I removed one of the rear brake drums and immediately saw that there was some mechnical damage to the magnetic ring at the rear of the wheel hub. In fact there was a 1 mm gap at one point on the circumference. This had obviously been the cause of the ABS kicking in as each time the gap in the magnet passed the sensor the ABS unit thought the wheel had locked.
I checked the other wheel and there was no similar damage to the magnetic ring.
I then realised that in order to fix this problem a new hub was required - it was not possible to replace the magnet. I purchased a new hub kit (including new nut) from Partco (Unipart) for £55 inc VAT. I also bought a torque wrench capable of 250 ft lbs of torgue (204 lb/ft required for the hub nut). I bought a pair of rear brake adjusters (as I had noticed the one on the other rear wheel was damaged also) from partsworld-uk.com for £32 or so.
I replaced the hub and adjusters last night and when removing the old hub noticed that there was a much greater amount of damage to the magnetic ring than there had been previously. Be careful when loosening or tightneing the hub nut - a quality wrench and socket are required. When tightening the nut the short socket extension actually twisted and sheared.
Casue of problem: It seems that, if the rear brakes are not adjusted correctly via the auto adjusters then the handbrake mechanism on the rear brake shoes will travel further than intended and eventually scrape against the magnetic ring on the hub - therefore casusing at least £55 of damage in a short space of time as the magentic ring is made of some sort of soft plastic.
After replacing the hub and adjusters it is important to repeatedly depress the brake brake pedal (with the handbrake off) to ensure correct adjustment of the brake shoes - do this at least 30 or 40 times or until you can't hear the click of the auto adjuster.
I've just replaced the fuse and tested the car and everything seems OK.
Sorry for the long post but this might save some of you a lot of messing about.
Tony
