Seized brake piston

[Posh Pete]

Doing a clean up and new pads on the 1100's Brembo's tonight. Offside caliper: no probs. Nearside: one feckin piston which will not push back no matter how hard I try! The other 3 are fine.

Tried mole grips across one of the old pads. No joy. The rubber handle of a pair of pliars as a lever. (The pistons are hollow at the top so care is needed I know!) No joy.

Any suggestions?

 

[Timolgra]

try blocking the 3 good ones and pumping the stuck one out a bit first with the brake lever.

 

[Voyager]

Doing a clean up and new pads on the 1100's Brembo's tonight. Offside caliper: no probs. Nearside: one feckin piston which will not push back no matter how hard I try! The other 3 are fine.

Tried mole grips across one of the old pads. No joy. The rubber handle of a pair of pliars as a lever. (The pistons are hollow at the top so care is needed I know!) No joy.

Any suggestions?

I once removed a stuck brake piston for a pal.

He brought me the caliper, I wrapped it in a towel - then applied 150 psi from my compressor down the bleed nipple hole.

There was a very satisfying bang and the piston came out undamaged. Then it was just a matter of carefully cleaning the bits with brake fluid and a cloth (nothing abrasive).

We fitted new seals and it worked fine thereafter.


You have to wrap it up though, judging from the noise, the piston could go quite a distance and do a lot of damage


Bob.

 

[ELIMINATOR]

Do not force it back in!

it is either suffering from corossion or the dust seals have swollen where corossion has got into the groove. At this point i should state I've never removed GS pisons and I'm basing this on other bikes.

You will need to move this stuck piston out and see if it is corroded, then you must clean this off, if you can.

As said earlier restrain the free moving pistons, so that the force of the hydraulics acts only on the one piston.

Shame you're not local, I've blown siezed pistons out at work, on our hydraulic pump that can go up to well over 1000 psi. This is safer than blowing compressed air through the caliper.....but fair enough, horses for courses, etc.

 

[Stewart H]

You need to get it out, sort the problem
(probably as Eliminator says)
I n your situation you will need a screwdriver handle to keep the two okay opposing pistons in place, then a small G clamp to keep the third "good" piston in place, now the pressure you are applying (I have a compressor for mine but pumping the lever slowly will do it) will push the stuck piston out, clean gunge, seals, using green pan scrubber and brake fluid, lube with red rubber grease if available, if not then brake fluid, refit, bleed, ride.

Stewart

 

[Taff]

..... Then it was just a matter of carefully cleaning the bits with brake fluid and a cloth (nothing abrasive).

A mechanic advised me to use Autosol.

 

[Voyager]

Further to my post above . . .

This was done two years ago and my memory isn't good

Thinking about it more . .

The caliper was a Brembo two-piston unit which we split. That meant I only had one half and one piston to deal with.

I closed the bleed screw, put a rubber sealing ring into the hole that connects the two half calipers and used the air blower on my compressor. I had to use body weight to keep it in place so didn't use anything like the full 150 psi.

The whole lot was wrapped in an old towel to contain the bits and to deaden the noise.

It worked.

A hydraulic pump would be far more controllable - but I don't have one (unless I connect it to a tractor ).

If you can't separate the caliper halves, the three good pistons will have to be clamped off.

Soak the stuck piston in brake fluid (after removing the dust cover) well before you start.


I'm not far from you if you want to bring me the caliper


Bob.

 

[Posh Pete]

Thanks for all the tips guys. I'll try freeing the piston tm night by blocking off the good uns and pushing out the stuck un.

Bit pushed for time as I'm off to Skye with some pals on Friday lunch time. So thanks for the offer Bob but shortage of time will probably scupper it. If I can't do it myself tm, I'll probably fire the caliper into Wilsons at Uphall on Thursday.

 

[Stewart H]

To bleed em I use a couple of big syringes and plastic pipe, but the last bit of air usually needs to come out overnight, dont forget to tie the lever back overnight to help
Stewart

 

[alimey4u2]

Fill with water, close the bleed nipple off, block the good ones & place in the freezer...No boom/bang/compressor/towels, just good ole material science..

 

[Posh Pete]

Thanks again for all the ideas folks.

I like the freezer one especially - simple but effective!

Anyway, I got the piston out tonight with the aid of a pair of mole grips and an old brake pad. The pad and grips kept the two opposed pistons in place while the neck of the grips stopped the third piston from moving. Lever pressure did the rest very easily. Wish I'd thought of that last night!

The seals look a bit dodgy and I'm running out of time, so I may pop it into the bike shop near my work to clean things up and fit new seals.

Phew!