Caliper pistion won't play nice

[joe]

After reading the awesome brake rebuild how-to by black_peter, I decided to take on the awesome task of rebuilding my front calipers. I was completely unprepared for the maelstrom I unleashed. Well, ok, it isn't that bad. I have one piston that refuses to exit its bore. The other 3 pistons are obedient.

I attempted the channel-lock hook method in the how-to with no success. I attempted to use air from a tire pump - no dice. The tire pump was responsible for getting the other three pistons to move. I have since attempted to re-assemble the calipers (minus brake pads) and refill the system with brake fluid. I have successfully bled the caliper and have tried pumping the MC several times, but to no avail. I have had to install vice grips on the other three pistons to keep them from completely popping out of their bores (don't worry, I have taken extra precaution to ensure the outside of the pistons are unscathed).

It appears to me that since this piston will not move, even under regular braking function, it has been inoperable for some time. This makes it all the more necessary for me to rebuild these calipers. I am hesitant to use the grease method mentioned.....and I figure if the normal hydraulic action of brake fluid will not manipulate the piston, grease may not have much luck either.

I apologize for the ramblings, but I would like to enlist any suggestions that may help me overcome this problem.


Thanks again for the help! Joe

[brian t]

buy a new caliper damn

[joe]

I would just as soon use the ones I have....they just need a little "persuasion"....that's all.

[rexazz2]

have you tried pushing the bad piston back in ?
maybe if it will move a little inward it will break loose

[steves]

I've always used about 40PSI out of my air compressor, a damp rag, and a nozzle.

Just have to be careful not to pinch your fingers.... ask me how I know.

[BradsKat]

I've always used about 40PSI out of my air compressor, a damp rag, and a nozzle.

Just have to be careful not to pinch your fingers.... ask me how I know.

I used a wood block/rag to "catch" the piston in case (when) it releases. And in case you missed what Steves said... WATCH WHERE YOU PUT YOUR FINGERS - it hurts like a mofo if you get dinged and you can seriously damage yourself.

[Teh_K]

If the piston has been inoperable this whole time, then the brake pad wear would be crooked for that pad.

Regardless, I've never seen one get stuck before, but if you're determined to keep the caliper and the piston won't come out even under normal hydraulic function, then I'd just sacrifice that piston and use the biggest set of clamps/pliers I could find and rip that puppy out (even if it means marring it).

The problem is... if it truly is stuck via metal-to-metal contact (like it's crooked or something), then the piston and caliper bore are probably already effed and marred, so you'd want a new caliper body anyway.

[steves]

My guess is, that he probably cocked it ever so slightly when attempting to remove it... and no gentle means will remove it.

[Astro4x4]

I vote it's crooked in the bore - push it back into the caliper to square it up, then have a go at removing it again to inspect for damage.

[joe]

ok, thanks for the input everybody. I'll monkey with it and see what happens.

[joe]

I think the piston was sitting crooked in its bore. In my desperation, I ended up using a folded up spark plug box as a "buffer" between my channel locks and the caliper body. I placed the edges of my feet on either side of the caliper and consistently pulled up on the piston. I'll be darned if it didn't work for all four of them and no damage to the pistons to boot.

Crazy desperation is the mother of a half-cocked solution that only works by the sheer grace of God.