is this a BAD idea (freeze water in caliper to POP piston)?

Hi All...

I'm not havng any luck getting the piston out of my 1978 KZ400 caliper...

I do not have access to an air compressor and and there is no "latch point" on the rim of the piston to pull it out with pliers (or anything)...

Also, i have not been able to find anything to stick it in the brake line hole to try and "pry up" the piston from the inside out...

(sure i could go the route of reconnecting everything, filling with brake fluid, and then try and "pump" it out)


but i was thinking:

- fill the inside of the caliper with water
- insert end screw (to keep water in)
- FREEZE IT!
- water expands upon freezing...
- POP! piston "could" come out

?

i'll be cleaning the whole thing once the piston is out, so i do not see any "down side" to giving this a try...

(well, unless of course the piston is ceased and the caliper cracks, but.... if the piston is ceases, the caliper is crap!)

am i missing something?

thanks...

- prime

Ummmmmm. I wouldn't think water would be a good idea (although I have never tried it).
I don't know if you would get enough expansion for it to happen.
I have had problems in the past with the air compressor.
But if you can push the piston in and blow it back out with the compressor, a few tries might get it out.
A co-worker had the same problem on his duals piston caliper on his Hond@. He hooked them back up and refilled with brake fluid and pumped them out.

YMMV.

A co-worker had the same problem on his duals piston caliper on his Hond@. He hooked them back up and refilled with brake fluid and pumped them out.

Compressed air is THE way to do it, but I agree that if not available, above is the way (yes, messy) to do it. Have done it accidentally a few times as a auto mech and it (unfortunatly) workes great! :dry:

I have done this a number of times using air from my el cheapo $20 electric air compressor (available at all auto suppy stores, and at Walmart). It plugs into any car cigarette lighter socket. You need to buy this.

Have always used the air-pressure method without needing to get more drastic. Next-best choice would be using the bike's natural brake fluid pressure.

Heard about but never tried either of these alternative methods which are statements made by others (not me).


Boiling water methods --

Get an old kettle, drop the caliper in and then fill with water and boil. When its boiled. you will be able to rotate the piston if you clamp in a vice. Works every time. Just removed some frozen pistons this afternoon using this method.

If I have trouble separating metal components, before resorting to heavy tools I reach for the kettle. Boil up a full one and pour the red hot water over the caliper. You should get differential expansion between the parts and this will help ease the parts apart. The reach for the air line quickly and you should have a result.

Grease gun method (said to be as dangerous or even more dangerous that the air pressure method) --

Remove the hose, fit a grease nipple, apply grease from grease gun. You can get enormous pressure on a grease gun and the grease helps lubricates things. I've only had this trick fail once, there was so much pressure the calliper casting split. I did once machine a piston out of a hideously expensive racing car calliper just to avoid damaging it, then had to sleave it anyway (the bore was corroded).

Used a grease gun. Sealed where the brake line hooks on with a banjo bolt. Grease gun fits right on the bleeder and just make sure the bleeder is open, then start pumping the grease.


Whatever you try, be extra cautious, please wear goggles, and stay out of the line of fire.

Good Luck!

Post edited by: Patton, at: 2007/12/07 15:31

Post edited by: Patton, at: 2007/12/07 15:32

Don't pry anything, you will harm the piston.
Here are two methods I know of that haven't been mentioned. This assumes the piston is locked in there pretty good, otherwise start with air pressure like above.

1:
Screw a bolt or plug into the inlet.
Take a mini grease gun and pop it on top of the bleeder.
Pump away.
Grease pressure will force out the piston.

2:
Drill a hole into the back of the caliper behind the piston. Pop out the piston with a wood punch. Then buy a tap and tap the hole you drilled and insert a plug with Loctite.
I would choose this method as a last resort.

Post edited by: OKC_Kent, at: 2007/12/07 15:35

If you can get a plug for the hose port which seals very well, just clean out the cylinder with a good degreser than poar in some baking soda about a table spoon would be good enough, than with a sirringe or something squirt in some vinigar, place and tighten the plug and hold it away from the body and point twards a soft place. It WILL come out. I used to do that in the old days before I had a compressor, when I still lived in the appartment.

this is going to be messy to clean up, but you can buy a grease fitting , put it in place of the bleeder and pump it with a greese gun, it will push the piston out

man most u guys are repeating the same thing over and over again...

i think the gease thing was said about 5-6 times..


u guys should probly read the posts and trying not to repeat everything over and over..

hi all...

well, i wish i had an extra old caliper to just try this ice thing on (as i think i could work), but... i'll keep chasing more conventional ways...

i apprecaite all the advice.

- prime

RollingStock wrote:

man most u guys are repeating the same thing over and over again...

i think the gease thing was said about 5-6 times..


u guys should probly read the posts and trying not to repeat everything over and over..

nah, only three times, but who's counting? Oh, you are...:huh:

I dont know if it has been mentioned, but I hear about people using a grease gun to pop the piston out. :laugh: :laugh:

I usually just reconnect the brake lines and use the brake fluid to push the piston out.
Never had any luck with an air compressor.
Fish