Advice re binding brake

[Toyoda]

I noticed one of my rear disc brakes was getting seriously hotter than the rest so jacked it up and sure enough, I was meeting a lot of resistance when turning the wheel by hand. Took it to the garage who told me that they found that the caliper slider was stuck fast so freed it up using heat, cleaned up the slider pins and they have covered it all in copper grease (which I now believe is totally the wrong grease to use)

Anyway, I picked the car up, drove home about 8 miles and the 'fixed' brake was boiling hot. Way worse than before! Jacked it up and now I can't move the wheel at all by hand.

I'm now not wanting to drive it anywhere further than a mile or so to the nearest garage, but what on earth could it be causing it to stick, given that it's supposedly been freed up?

Edited by Toyoda on Monday 21st August 18:26

[lucido grigio]

If the sliding bits have been freed off then the other thing is a sticking piston.

A new caliper is probably best move and you're right to not drive too far as sticking caliper equals heat transferred to brake fluid

and loss of pedal.

[Toyoda]

He said the piston was OK but who knows. Not sure if its relevant, but when I jacked it up, I was able to turn the affected wheel a little bit by hand then all of a sudden it went really stiff and wouldn't turn.

[tapkaJohnD]

The other reaosn for a 'stuck' piston is a hose that is going internally.
If it delaminates, then the lining can forma one way valve that prevents the return of fluid from the piston.
A new hose iwon't cost much - worth a punt?

JOhn

[GreenV8S]

It could easily be a worn or damaged slider which was not fully corrected by the cleaning they did. The fact they found the slider seized proves that this was the cause of the original problem and it's safe to assume that it's the same problem causing the calipers to drag now. The brakes may release themselves when they cool off, but if they're still dragging you would probably be able to confirm the sliders are stuck if you take the wheel off.

[Its_the_Dacia_Sandero]

I had this issue with my previous Mitsubishi. The handbrake mechanism wasn't releasing and was holding the pads against the disc. After a great deal of faffing about I got a second hand caliper which solved the problem. Make sure you change the brake fluid as it will have overheated and degraded.

[Toyoda]

Thanks for the replies.

My apologies, I seem to have been hasty in saying the wheel wouldn't spin by hand. Mustn't have jacked it up enough. I've now been out for multiple drives and jacked it up a couple of times and the wheel does spin much more freely. However.... the disc is getting excessively hot under normal driving. The brake doesn't appear to be binding/stuck on, as I've driven for a few miles barely touching the brakes and after checking the disc it's lukewarm, like the other discs, but as soon as I start driving and braking as normal, the affected rear disc gets very very hot, much hotter than the other rear, and even hotter than the fronts. Could it be that following the repair, the caliper/slider is now so freed up that the brake is working almost too well, and somehow taking the priority of the braking force when I depress the pedal? I suppose it would have made sense to grease up all of the calipers rather than just this one??

[Its_the_Dacia_Sandero]

How's the bearings? Are they loose? Do the bearings have any grease left in them? Heat can be generated by worn or dry bearings which will eventually cause them to seize.

[HustleRussell]

OP you've got a jack, why not whip off each caliper in turn, wire brush the carriers, degrease everything (removing that coppaslip), thoroughly clean the pins and reassemble with the correct grease.

[GreenV8S]

Toyoda said:

Could it be that following the repair, the caliper/slider is now so freed up that the brake is working almost too well, and somehow taking the priority of the braking force when I depress the pedal?

No. There is a fault preventing the pads from releasing fully when you stop applying the brakes. Since it only affects one corner I would assume the problem is at the affected caliper or the hose leading to it. Since your garage has already found evidence that the slider was sticking (to the extent they had trouble releasing it) I think it is safe to assume you have the same problem now. It is vanishingly unlikely that you have two different problems causing identical symptoms on the same caliper.