Caliper piston getting nackered

[-Matt-]

Hi all

Just did my first ever brake service/clean at home - took me a mammoth 5 hours total hopefully be a bit quicker next time round ...

I noticed one of my pistons on the front right caliper is a bit stiff [had to hold the others to get it to come out and then it was a bit slow and doesn't quite go back in as far as the others].

This is causing [as has been the case for a few months] very slight rubbing sound when the wheel is turned were i think the pad isn't quite going back as far as it should.

Is this something i particularly urgently need to get sorted or as the pad wasn't noticably worn more than the others and the wheel still turns fine etc could i leave it a few months without any problems.

Just spent the last 2 weeks servicing everything don't really fancy servicing the caliper too just yet if i can avoid it

Cheers all

[.....]

Hold the other pistons in with a bit of wood and pump the sticky piston out. Clean it with brake cleaner or brake fluid and push it back in - you may have to use a G clamp to help you get it back in. Then pump it out, clean and repeat until all pistons are moving freely together.

If this doesn't work then it could be time to pump the piston out, remove the seals, clean out the crud and rebuild.

[-Matt-]

Thanks for the reply. I pumped it in and out a few times but didnt seem to fix it really so i guess perhaps needs a rebuild :/ its been like this rubbing a bit for months so do you think i should get it done particularly urgently or could it be left longer with just the risk of slightly increased pad wear?

Cheers

[mentalboy]

If it's stiff and not returning it will rub hard on disc all the time you are moving.
This means increased pad wear, drag slowing you down and therefore increased fuel consumption
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[Islander]

You'll have reduced braking efficiency too. Time for a rebuild - new seals, clean the crap out of the seal grooves, clean the piston up, a touch of red rubber grease, reassemble and bleed.

[-Matt-]

Guess id better crack on with it then ..

Is it fairly straight forward if you know how to bleed/change pads already, just slotting in new seals relube piston and push it back in?

To get the piston out you just literally pump it over a bucket til it and the fluid comes out i presume ?

Leaving the other set of pads in shouldnt matter should it also, hate trying to get the damned pad pin through takes me ages

Cheers guys

[mentalboy]

That's pretty close, yes.

Remove caliper. If you can restrain good piston it would be better or you'll just push that one out and leave the stuck one in. If you've got access to a drill, you'll need two 3mm(min) plates of steel, with two holes wider than the caliper drilled in them. Then use them to clamp in good piston, using two random bolts through holes.
It is best to replace seals on all pistons on caliper and unless you've got access to an airline then it's a bit of a faff but the safest way is to sort out one side then bleed brakes and do other piston(s). You could grab the lips of the pistons with mole grips (add padding) but you don't want to garb more than 2mm of the piston depth or the scuffs caused by mole grips will stuff your new seals later on.
If you've got twin discs it'd be advisable to then do the other caliper, as the likelihood is that the whole lot is in desperate need of a good clean up if one piston has started to jam up.

Some main seals have the barest of taper on them, but a close inspection of their seat is usually enough to suss which way in they should go.

Technically it is simple!
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