ABS working all the time (C250D)

[steve kane]

Hello, I have been trawling through the brakes section looking for clues to our C250D ABS problem, the brakes were just fine before we left the car standing for nearly a month, after this we found that the brakes were juddering, I initally thought it was just a little rust on the discs but it has not cleared and were begining to think that the vibrating is the ABS working everytime the brakes are applied, the pulseing can be felt through the pedal as well as the car genrally, there are no warning lights showing and the car pulls up nice and straight when not holding the wheel, the "bumping" from the brakes is related to speed in that it quickens with the speed of the car but I assume this would be the case with the ABS, is this right?? I feel its likly to be related to an ABS fault as I cannot see why the discs would have warped whilst just sitting for 4 weeks? but I would wellcome any ideas suggestains.
One thing I would like to do is to disable the ABS and test the brakes without any possibility of the ABS operating, Im going to look at my Haynes but I have to say that I dont think its one of the finest offerings, does anyone know if there is a safe way of doing this (ie withough frying some expensive bit of electronics that no one has ever heard of!!) is there perhaps a fuse I can pull, all replies greatly appriciated,
Steve.

 

[television]

One thing you cant do is to disconnect the ABS, as the car would fail its MOT. I do not think that you have a ABS fault. I think that you will find that one of the disc has rusted or mabe split. I left my car at Stansted for 4 weeks after driving through salt and snow. When I returned, one of the rear disc had split, they are made of cast iron. Have you tried driving the car any distance since.

Malcolm

 

[jberks]

the "bumping" from the brakes is related to speed in that it quickens with the speed of the car but I assume this would be the case with the ABS, is this right??

Agree with Malcolm, wrong - I'm afraid. Actually I'm not afraid, as whatever the fault, its probably going to be cheaper than your anticipated ABS problem. Problems related to speed are down to something turning, so brake disks, tyres etc. The ABS pulse is constant, whatever the road speed. It also feels a lot different to what you describe. You can prove this, go to a quiet road, take it up to 40 and stand on the brakes, then you'll know what ABS feels like for comparison.

 

[clive williams]

My first reaction to the symtoms would be to check all the brake discs/pads thoroughly and then ensure that the pistons are free to move. This will mean removing the pads on each caliper. It all sounds like a partial siezure. Check also the handbrake drums as if the handbrake has been left on for a month (not a good idea) it too could be partially siezed. Once you are absolutely positive the brakes are functioning correctly then look at the delivery/ABS system

Clive

500E
E320CDIT210

 

[steve kane]

Many thanks indeed everyone, it was raining here today so tommorow I will take a look at it, I had a quick look at prices for Discs and there seem to be a lot abound at about £30 a pair, mine are the Solid unvented type, so not too expensive, Im still at a loss as to why the brakes would go so "wobbly" whilst just sitting doing nothing, but as were pretty sure the thumping freq is speed related then it does seem from what people are saying that it cannot be the ABS which runs at a constant speed, still if I cannot seem anything clearly amiss I would still like to disable the ABS and see if this makes any difference on a test drive, does anyone know how to do this? once again, many thanks for your help,
Steve.

 

[television]

Many thanks indeed everyone, it was raining here today so tommorow I will take a look at it, I had a quick look at prices for Discs and there seem to be a lot abound at about £30 a pair, mine are the Solid unvented type, so not too expensive, Im still at a loss as to why the brakes would go so "wobbly" whilst just sitting doing nothing, but as were pretty sure the thumping freq is speed related then it does seem from what people are saying that it cannot be the ABS which runs at a constant speed, still if I cannot seem anything clearly amiss I would still like to disable the ABS and see if this makes any difference on a test drive, does anyone know how to do this? once again, many thanks for your help,
Steve.

You can unplug your ABS module, but it will not help your problem.

Malcolm

 

[steve kane]

Many thanks Malcolm, I expect your right, it might just be handy to know the other options just in case, I will however let you all know what I find,
once again, many thanks,
Steve.

 

[niva441]

Have you checked whether the discs have warped?

I've experienced similar in an old escort.

 

[steve kane]

The problem is solved,,,the car had been parked for 4 weeks, the handbrake was not on, however when my wife drove it away for the first time she reported a heavy clunk from the car, as though the brakes were stuck on.
On checking the rear discs I discovered two small areas which clearly looked like somthing was rubbing, however on closer inspection I could see that this was patches of glazed material on both discs, which was quite easily scraped off with a sharp screwdriver, I think that the Pads had stuck to the Discs through just being in light contact with them, the small layers of disc material, instead of being wiped off during several fast runs and heavy breaking were in fact baked on, I guess it would have eventually worn off, but Im happy to have solved the problem without resorting to great trouble and expense. I hope this might prove useful to somone else in the future and thanks once again for all your helpful sugestains,
Steve.