Caliper rebuild headaches...

[dgagne]

Well I have all the pistons out but one! I have soaked it in everything imaginable but one piston will not come out.

Any suggestions or things that have worked for others that have attempted this painful project?

Cheers,

Derek

[Jon Sailer]

I just put a block of wood in the middle that prevented both pistons from completely ejecting from the caliper. I was able to pressurize it with compressed air. I was actually able to do it with a tiny DC inflator at the track too. Then once they are close to being out, you should be able to pull it out completely. Well at least thats my experience and hope it helps.

[Emission]

Will it move at all? Has it moved a bit?

Try more air pressure, but expect it to really fly - so put wood and a towel around it.

[MotoSook]

You'll have to put the mating piston back in the caliper, then do as Derek suggested, block the the mating piston so there is more room for the stuck piston to come out further.

You may have to push the stuck piston into the caliper. Then do the above. Pushing it in will allow it to move out a little before it hits the spot when the seal and piston grab each other....repeat...push in, pressure, repeat.

[dgagne]

It is all the way in and has not moved at all...

Used compressed air, block of wood on all other three calipers, worked fine, this one piston is stuck in there.

Is heating it an option - I know brake fluid is flamable...

[Emission]

Can you use a C-clamp (with a piece of plastic on it so you don't mar the piston) to move it either way? If it is really all the way seated, as it sounds, that won't work.

Was this piston frozen to begin with? Is it corroded?

[MotoSook]

You might try to rotate it with channel locks. Grab exposed (do not damage the OD of the piston) lip. It's most likely corroded and not sliding well on the seal.

[dgagne]

Used a C clamp on the other free ones to hold them in, this one is all the way in and cannot grip it with anything.

Any thoughts on tapping in the center of it since it is a hollow piston to try and move it? Will this damage it?

[Emission]

Originally posted by dgagne
Used a C clamp on the other free ones to hold them in, this one is all the way in and cannot grip it with anything.

Any thoughts on tapping in the center of it since it is a hollow piston to try and move it? Will this damage it?

I'd tap it. Don't beat on it.

The last thing you want is to mar the piston.

[MotoSook]

No no...take the clamp off the other one. Try to rotate the stuck one so you get it unstuck...do it w/o pressure...the piston is probably corroded and bitting into the seal...patience.

[Emission]

Originally posted by Souk
"...patience."

That's the key here.

[DonMo]

You might want to try some PBBlaster and let it soak in a little. It has a wicking action so it might put you over the edge. Definitely sounds corroded.

[GeorgeK]

Put the other piston partway back in, fill the caliper with water and close all the fluid exits (use the bleed screws). Then compress the one good piston (c clamp, vise, whatever). the other one will come out, hydraulic press principle.

[Dionikes]

I was in your shoes yesterday. First, thing we (my Dad was assisting me) tried to do was to get it to spin it just a bit. We used a channel lock...a large one. From there one person kept teh air pressure connected while the other pried on the piston head with a screwdriver or large gasket hook. The combined efforts popped it off but it still took a while. Patience adn good luck.

[rlane]

GeorgeK's idea is a really good one, wish I had known that when I went thru this. Otherwise PB blaster "bath" persuasion with C-clamp or channel locks and plenty of airpressure> IOf the pistons are caked with "gunk" I had great results with Googone and a kitchen (nylon) scouring pad.

[DaveE]

I've sometimes had success hitting the caliper with a hammer behind the stuck piston with it under air pressure and soaked with penetrant. The shock or vibration seemed to loosen things a bit. Good luck.
Dave

[Biff]

You can push the piston all the way in and then have them glass beaded. This will eliminate the corrosion around the lip and it should pop out with all the other suggestions....pb blaster soak, in & out with air pressure a couple dozen times till it comes out!

[dgagne]

Great suggestions guys. I really like Georgek's idea, I will try it as long as I can find a bolt to close the opening where the brake line attaches.
Cheers,
Derek

I will let you know if I get it!

[Nine9six]

Originally posted by GeorgeK
Put the other piston partway back in, fill the caliper with water...

Better make damn sure you get all the water out before you rebuild, otherwise you will wind up with the same corroded situation. Remove as much water as possible using compressed air, then drop the caliper in the oven at 250 for a couple hours. This should remove any remaining moisture.
Best of luck to you...

[Neilk]

Originally posted by dgagne
Great suggestions guys. I really like Georgek's idea, I will try it as long as I can find a bolt to close the opening where the brake line attaches.
Cheers,
Derek

I will let you know if I get it!

I think the bleed screw from an S caliper would work. If you use a non-tapered bolt, you might damage the mating surfaces where the brake line meets the caliper.