Hopeless brake piston?

So I get the brake caliper off. The piston will NOT budge. Looks like the PO tried to use vise grips or monkey wrench or something to twist and pull the old piston out. So I'm guessing I will have to get the new piston. My immediate need is help on getting the stuck one out. Any good suggestions??

 

Grease gun, screws directly into bleeder screw, a few pumps, will come out, be sure to protect piston with a thin block of wood, I have done this may times, do not use compressed air or heat, gun will generate thousnads of psi.......................let me know how it works

 

i can tell you a real bad way, depending on how nuts you are but it will be out, most likely gone also
find a bolt to fit the brake line hole (8X1.25 i think) put about a shot glass of water in it, tighten the bolt, TAKE IT OUTSIDE, set it on something that won't burn, position a board above it, place a propane torch to blow on it, stand back a safe distance then back up some more, when the water boils the piston comes out, fast loud and hard
there's safer ways but their not as fun

 

Polock...that sounds like some needed entertainment, esp considering the crappy breaking of written agreements some people have on this board when parting out a bike...could be some good stress relief.

Going to try the grease gun now gari since my neighbors may not revel in loud noises as much as I would at 10:30 at night.

 

you guy's ain't no fun
you should try to make loud noises at least once a week then the neighbors get used to it

 

Got it out, thanks Gari.

My neighbors are vengeful like me :evil:

 

"The Steam Technique"

ROTFLMAO-BNITS !!!

 

I use comp' air, just got 2 stuck pistons out this week, I cut a long timber wedge, a foot long, tapering fron 1/4 " to 1 1/2 ", jut give it a blast, then move it along a bit, the last blast does give a satisfying pop.......

 

satisfying pop, come on now, i'am talking about run in the house and turn off all the lights before the cops get there ! "i was sleeping on the couch, i didn't hear anything officer "

 

You know us Brits don't get too excited with the odd explosion.

 

+1 on the compressed air. and a small peace of wood just think enough to leave a LITTLE room for the piston to pop out.

if it's stuck. i fill the inside with brake cleaner. if that don't work i go to WD. if that don't work i go to solvent cleaner and let it sit.

i've been known to use heat also. just enough to warm it up.

 

Polock we got to party

 

Personally, I've never had much luck with compressed air; and I've never tried the "steam cannon." I've used the grease gun trick many times with great success, but it is rather un-spectacular.

Back to the original question: Clean the piston up and carefully inspect it. As long as any pitting or "teeth marks" are not in the area swept by the seals, then you can re-use it.

This piston, for instance, was perfectly serviceable; the pitting you can see is above where the seals ride:

 

You can get away with pitting pretty much anywhere on the piston, as long as the 'pit' is less than 3mm wide.

 

What, is it "pee in Fitz's cornflakes" day?

The pitting on the piston in my pic, if in the main seal area, would be severe enough to leak.

Granted some pitting, just luckily placed in non-strategic places, won't leak because the piston moves such a very small distance; whereas if it had a 3/8" stroke it would be all over.

But the "judgement call" between what will work and what won't takes an experienced* eye like yours or mine; 'tis better in my way of thinking to recommend on the safe side rather than tell somebody it's OK to use a ratty piston with disastrous results.

The piston in the pic is currently in my '81 and has a bunch of miles on it (would have to look at log) with no issues; but had those pits been in the seal-swept area I would not have used it myself.

You are correct; I just prefer safe over chance.


*Old Fart's

 

Jeff, great to hear piston is out, set piston in lathe, spin at a slow speed, polish/smooth out imperfections with long strip of emery cloth, working up to a very fine #1500..to a mirror finish

 

Thanks for the advice guys...thinkin I'm just going to order a new piston...I don't have a lathe or any way to turn it down accurately. I'll give Chacal a shout, he's already hooked me up with some parts.

 

Just wondering why no one likes to pop the piston out with the fluid that's already in the system?
I know your limited to doing one calliper at a time... but its damn easy.

 

Just wondering why no one likes to pop the piston out with the fluid that's already in the system?
I know your limited to doing one calliper at a time... but its damn easy. <quote>
It's much more expensive than air. ;o)

 

But...

at least you'll get one out with the fluid that you'll drop...

alright you got me on that one Brake fluid does cost more than air!