Brake only sticking on in forward direction, possibly?!
Discussion
Hi all,
Right rear brake is getting hot and starting to bind, and I cannot pinpoint why.
Car is a Mk2 S-Max, so a Mk5 Mondeo with a fancy top on it.
-Electronic handbrake that acts on the rear normal pads, so only one set of pads.
-Parking brake is working nicely, pull the switch and it locks the wheel, release the switch and each wheel sounds similar, and the car rolls.
-Pads are admittedly getting thin - and will be changed when I have fixed the problem.
-I have cleaned the pads, they all move freely in the calipers.
-All 4 rear pads are worn the same amount and worn evenly.
-I have polished the slide pins and lubed them up slightly, the caliper floats freely when I move the disc.
-The two rear discs are smooth, do not have any pad buildup on them - they are solid 11mm thick 316mm diameter discs.
-(discs will be changed with the pads when I have fixed the problem as they have a small lip and have now been rather heated(I have measured 350 deg C, and that was not the day the brakes were smoking))
-I have wound the electronic handbrake mechanism all the way back to service position with a 9V battery, smooth operation all the way.
-I have pushed the pistons in and out a few times, again the moved smoothly.
-I flushed the brake fluid 8 months ago, routine service, fluid was black coming out, car had been fine and was fine until a week ago.
-I have swopped right and left pads, still the right wheel overheats.
-I have swopped right and left discs, still the right wheel overheats.
-I have checked pads for contamination and lightly filed the tops - they behaved as normal brake pads.
-I have rubbed my fingers across the brake pad, if I rub it as though the car was going in reverse, it feels smooth, if I rub it as though the car is moving forwards it feels like splinters that stick out of the pad and into my fingers, but the right side still over heats after I moved these pads to the left.
-Potentially non-related, I feel I am having to really press on the brake to get the car to stop recently, however I can still get the fronts to lock up / ABS if I stomp on the pedal.
Still, if I take the wheel off, I can turn the disc backwards with minimal resistance, but binds up when I try turn the disc forwards (so clockwise as I look at it)
Any ideas where to look next?!
Right rear brake is getting hot and starting to bind, and I cannot pinpoint why.
Car is a Mk2 S-Max, so a Mk5 Mondeo with a fancy top on it.
-Electronic handbrake that acts on the rear normal pads, so only one set of pads.
-Parking brake is working nicely, pull the switch and it locks the wheel, release the switch and each wheel sounds similar, and the car rolls.
-Pads are admittedly getting thin - and will be changed when I have fixed the problem.
-I have cleaned the pads, they all move freely in the calipers.
-All 4 rear pads are worn the same amount and worn evenly.
-I have polished the slide pins and lubed them up slightly, the caliper floats freely when I move the disc.
-The two rear discs are smooth, do not have any pad buildup on them - they are solid 11mm thick 316mm diameter discs.
-(discs will be changed with the pads when I have fixed the problem as they have a small lip and have now been rather heated(I have measured 350 deg C, and that was not the day the brakes were smoking))
-I have wound the electronic handbrake mechanism all the way back to service position with a 9V battery, smooth operation all the way.
-I have pushed the pistons in and out a few times, again the moved smoothly.
-I flushed the brake fluid 8 months ago, routine service, fluid was black coming out, car had been fine and was fine until a week ago.
-I have swopped right and left pads, still the right wheel overheats.
-I have swopped right and left discs, still the right wheel overheats.
-I have checked pads for contamination and lightly filed the tops - they behaved as normal brake pads.
-I have rubbed my fingers across the brake pad, if I rub it as though the car was going in reverse, it feels smooth, if I rub it as though the car is moving forwards it feels like splinters that stick out of the pad and into my fingers, but the right side still over heats after I moved these pads to the left.
-Potentially non-related, I feel I am having to really press on the brake to get the car to stop recently, however I can still get the fronts to lock up / ABS if I stomp on the pedal.
Still, if I take the wheel off, I can turn the disc backwards with minimal resistance, but binds up when I try turn the disc forwards (so clockwise as I look at it)
Any ideas where to look next?!
Peanut Gallery said:
binds up when I try turn the disc forwards (so clockwise as I look at it)
Start there. There's no obvious reason for the brake drag to be sensitive to the direction of rotation. Do you get similar direction-sensitive drag on the other rear wheel? If you can reproduce this with the wheel off then hopefully you can diagnose the cause. For example it might be an overly tight wheel bearing.
If you're comfortable taking the caliper off, see whether it still happens with the caliper off - for all we know it might be some other component that's dragging.
GreenV8S said:
Start there. There's no obvious reason for the brake drag to be sensitive to the direction of rotation. Do you get similar direction-sensitive drag on the other rear wheel?
If you can reproduce this with the wheel off then hopefully you can diagnose the cause. For example it might be an overly tight wheel bearing.
If you're comfortable taking the caliper off, see whether it still happens with the caliper off - for all we know it might be some other component that's dragging.
Good call, I will pull both wheels and compare, I might try swopping the brake caliper mounting bracket, this houses the pads and see if it has worn in such a way to push the pads into the disc like a leading brake shoe on a drum.If you can reproduce this with the wheel off then hopefully you can diagnose the cause. For example it might be an overly tight wheel bearing.
If you're comfortable taking the caliper off, see whether it still happens with the caliper off - for all we know it might be some other component that's dragging.
Will update, thank you!
You've not swapped the pad carriers side-to-side... worth a stab if they're not handed.
If you're turning the discs with the wheels off, spin a couple of wheel nuts on to ensure that the disc is held flat and tight to the hub flange.
Also, mount the calipers to the pad carriers without any pads and check that they slide smoothly over their full range. I've had twisted carriers before where each slide was fine individually, but not when both tightened up, as they weren't parallel.
But a binding problem could be hydraulic, not so easy to 'see', perhaps a hose that's developed into a 'one-way valve' internally.
If you're turning the discs with the wheels off, spin a couple of wheel nuts on to ensure that the disc is held flat and tight to the hub flange.
Also, mount the calipers to the pad carriers without any pads and check that they slide smoothly over their full range. I've had twisted carriers before where each slide was fine individually, but not when both tightened up, as they weren't parallel.
But a binding problem could be hydraulic, not so easy to 'see', perhaps a hose that's developed into a 'one-way valve' internally.
Edited by TwinKam on Friday 17th May 21:58
Edited by TwinKam on Friday 17th May 21:59
Update time, TL:DR - problem fixed, and I need a new wallet.
With your ideas combined, I set about to look for any rust on the carriers / caliper that might be causing the issue.
Carrier off, cleaned, it was as straight as I could see. tiny bit of rust, but nothing I would worry about, cleaned.
Caliper - there was a potential lump of rust that would push the pad against the disc, causing the pad to push forwards, causing the pad to push against the disc - I set about removing this, then noticed the boot had a small split, so some investigation later I decided to extend the piston, give it a polish, and re-assemble. (The small split turned into a large split in the bit that I could not see)
Well, that did not go to plan, and the wormscrew of the electronic handbrake decided to end up as a pile of ball-bearings and springs as a pile in the caliper.
Water had got in around the rubber and had caused some rust so it made the piston stick right at the point where the pads were touching the discs, so that would not have been helping the situation.
One trip to Ford, one new caliper, and all sorted - new pads, discs and another brake fluid flush coming.
With your ideas combined, I set about to look for any rust on the carriers / caliper that might be causing the issue.
Carrier off, cleaned, it was as straight as I could see. tiny bit of rust, but nothing I would worry about, cleaned.
Caliper - there was a potential lump of rust that would push the pad against the disc, causing the pad to push forwards, causing the pad to push against the disc - I set about removing this, then noticed the boot had a small split, so some investigation later I decided to extend the piston, give it a polish, and re-assemble. (The small split turned into a large split in the bit that I could not see)
Well, that did not go to plan, and the wormscrew of the electronic handbrake decided to end up as a pile of ball-bearings and springs as a pile in the caliper.
Water had got in around the rubber and had caused some rust so it made the piston stick right at the point where the pads were touching the discs, so that would not have been helping the situation.
One trip to Ford, one new caliper, and all sorted - new pads, discs and another brake fluid flush coming.
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