Rear Caliper Locking
Discussion
Hello,
I have an issue where the rear passenger brake will start to engage and bind when driving after pressing the brakes a few times.
So this evening I pulled the fuse from the ABS as I was confident that the calipers were fine and I replaced the line on saturday.
Voila, the issue is gone and the rear passenger no longer locks.
I stopped the car and replaced the ABS fuse and slowly the issue returns after pressing the brakes lightly a few times. Then when it starts happening and you slow the car to very slow it starts trying to bind harder and will bring the car to a stop. You can drive on if you accelerate as the brakes on the other three wheels are not on. But it is trying its hardest to stop you.
So the question is - is this the abs wheel sensor and if so would this tell the abs to lock one wheel or would it try to engage on all 4 wheels or.....
is this air in the abs module causing the locking of one wheel?
I say air in the abs as I recently changed the master cylinder but this only started happening a few weeks after the master cylinder change and everything has been fine until now since the change.
So have I answered my own question? it is the sensor? but would the abs module try to lock one wheel only?
Barry
I have an issue where the rear passenger brake will start to engage and bind when driving after pressing the brakes a few times.
So this evening I pulled the fuse from the ABS as I was confident that the calipers were fine and I replaced the line on saturday.
Voila, the issue is gone and the rear passenger no longer locks.
I stopped the car and replaced the ABS fuse and slowly the issue returns after pressing the brakes lightly a few times. Then when it starts happening and you slow the car to very slow it starts trying to bind harder and will bring the car to a stop. You can drive on if you accelerate as the brakes on the other three wheels are not on. But it is trying its hardest to stop you.
So the question is - is this the abs wheel sensor and if so would this tell the abs to lock one wheel or would it try to engage on all 4 wheels or.....
is this air in the abs module causing the locking of one wheel?
I say air in the abs as I recently changed the master cylinder but this only started happening a few weeks after the master cylinder change and everything has been fine until now since the change.
So have I answered my own question? it is the sensor? but would the abs module try to lock one wheel only?
Barry
Hi,
I only saw the replies to my post this morning so thank you.
It is a 2002 Seat Toledo MK2 1.9td and I do not have VAGCOM.
It has been suggested that this is a sticky valve in the ABS as one wheel is affected and I agreed to an extent but.....
UPDATE
The brakes worked well but there was binding on one wheel but there was another issue where no fluid would flow to the rears when bleeding, (fluid would come out when the pedal pressed but not of its own accord), and indeed when you disconnected the two pipes coming from the MC to the ABS there was no fluid flowing from them either (again would flow when pedal pressed). This suggested a blockage of some type in the MC. The binding could still have been an ABS issue as it affected only one wheel? Or could it have been a return issue where fluid is not allowed return properly after the pedal is released but I read somewhere that this would have affected at least two wheels and not one?
Anyhow, I found the cause of the non flow. The bottom bolt on the MC was too tight against the servo and so pushing the piston in a fraction too much. As soon as I loosened it just a bit fluid started flowing. So one issue resolved.
I also removed the ABS and used compressed air and brake cleaner through the ports to blow out any crud and clean the valves.
I am hoping this will be my problem resolved but will not know until tomorrow.
My question is whether the problem at the MC could cause the binding at one wheel or did I indeed have two separate issues?
Barry
I only saw the replies to my post this morning so thank you.
It is a 2002 Seat Toledo MK2 1.9td and I do not have VAGCOM.
It has been suggested that this is a sticky valve in the ABS as one wheel is affected and I agreed to an extent but.....
UPDATE
The brakes worked well but there was binding on one wheel but there was another issue where no fluid would flow to the rears when bleeding, (fluid would come out when the pedal pressed but not of its own accord), and indeed when you disconnected the two pipes coming from the MC to the ABS there was no fluid flowing from them either (again would flow when pedal pressed). This suggested a blockage of some type in the MC. The binding could still have been an ABS issue as it affected only one wheel? Or could it have been a return issue where fluid is not allowed return properly after the pedal is released but I read somewhere that this would have affected at least two wheels and not one?
Anyhow, I found the cause of the non flow. The bottom bolt on the MC was too tight against the servo and so pushing the piston in a fraction too much. As soon as I loosened it just a bit fluid started flowing. So one issue resolved.
I also removed the ABS and used compressed air and brake cleaner through the ports to blow out any crud and clean the valves.
I am hoping this will be my problem resolved but will not know until tomorrow.
My question is whether the problem at the MC could cause the binding at one wheel or did I indeed have two separate issues?
Barry
barrymurphy said:
The bottom bolt on the MC was too tight against the servo and so pushing the piston in a fraction too much. As soon as I loosened it just a bit fluid started flowing.
The master cylinder should be tight to the servo. The true cause of the problem is probably that the pushrod from the pedal is adjusted too long. You need to correct that and make sure the m/c is secured properly.agreed. thanks.
This was a second MC, not the original but it was the same model number.
There must be a minimal difference between the two on the travel of the piston in the MC.
It is minimal because as soon as I cracked the nut loose, fluid flowed,
Are the push rods adjustable on all boosters? I was toying with the use of a thin washer on the bottom bolt as I am not sure if the push rod is adjustable or not.
If it is I will go that route.
Thanks
This was a second MC, not the original but it was the same model number.
There must be a minimal difference between the two on the travel of the piston in the MC.
It is minimal because as soon as I cracked the nut loose, fluid flowed,
Are the push rods adjustable on all boosters? I was toying with the use of a thin washer on the bottom bolt as I am not sure if the push rod is adjustable or not.
If it is I will go that route.
Thanks
and whilst I know the MC should be tightened I do remember getting the impression when tightening the bottom bolt that I could conceivably have kept tightening, all be it with effort. It is a while since I did it but I vaguely remember getting the impression that you could keep tightening and deform/squash the servo/booster? hence I stopped.
Is this the case and that is in fact what I have done just by a hairs length?
I am not at the car at present and will check this later.
Is this the case and that is in fact what I have done just by a hairs length?
I am not at the car at present and will check this later.
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