Stuck brake caliper piston

Hi XJ

Just had my front calipers off to clean pistons as braking erratic, and when tried to 'g-clamp' them closed again, front right will not budge!
Front left closed up no problem, but right one won't move. Can't reassemble to test.
Anybody got any ideas, who's encountered similar?
Thank You!

 

If your braking was erratic, chances are you need to rebuild the calipers. The piston may not have been working properly. Not too difficult and worth the effort. You can find the rebuild kits on ebay or online stores like Partzilla. They are usually around $25 or so. And if you've not done it before you'll need air pressure to pop the piston out. Just make sure you're not in the path cause that thing can come out like a rocket.
Just recently rebuilt all three calipers on a bike that's been sitting a long while and you can't believe how much crud that can accumulate on those pistons.

 

+1 new seals after a cleanout make these suckers glide. (so to speak)

BTW: I find that keeping something in between the break pads, if your changing the wheel out is a great idea. Pulling the lid off the master cylinder helps to push them open if you need to push the brake fluid back up into it also of course.

 

If air pressure won't budge the piston , a grease gun threaded into the brake line fitting it will push piston out , downside it is messy and you have to ensure all grease is cleaned out.

 

Thanks for your replies and advice.

Got the offending piston out, (just manoevered it out), and noticed some pitting on edge of piston wall where groove is. The rest seemed relatively clean. Cleaned it all up anyway, and reinstalled, refilled with brake fluid, and bled the air out.
Went over to do the left side, and the brake fluid bleed nipple is rounded (see pic) Be grateful if anyone knows of method to remove it. (heat?) Tried freeze spray, no joy.
Took it out to test brake and although better, still not as it should be (?)
Realise I need to rebuild these calipers (the bike is 40 years old now, and don't know the full history of brake maintenance, apart from my own, changing pads etc.) but to do both, I need to get the nipple off on left-side caliper.
Any suggestions please?

Kind regards.

 

Here is an idea......take a hammer and a drift, lay the end of the drift on the side of the boss the the bleeder screws into, wack the drift with the hammer a couple of times; also get a 6 point 8mm socket that you can get on the bleeder, might have to tap in on.

Hope this helps

 

Just use some vise grips. Even channel locks should work if you don't have vise grips.

 

freeze spray computer duster upside down the whole can . let it thaw out. then penetrating oil down the hole and around the threds. then an 8 point socket a long one tap it onto the bleeder all the way down to the caliper then tap socket 100 times with a small hammer to shock it .

 

Vise grips. It’s already destroyed so you’re gonna replace it anyway

 

^^This^^

 

I find these very effective if its already trash and will be replaced. Not sure if the depth would be enough though.

 

Or just stick an easy-out down the hole

 

How old are your brake lines? If more than 5 years old, you may have an issue of the brake line disintegrating inside and fouling the brake fluid, and gumming up the caliper.

I used to have to disassemble and clean gummed up and sticky front brake calipers all the time until i changed brake lines

 

Issue resolved. New piston and oil ring installed in left hand caliper - much better, but right may need some attention also. Shall probably replace piston in that too.
Thanks to everyone who contributed!
Kind regards.