Stuck brake piston

[lukemillar]

Rebuilding my calipers and 7 out of 8 brake pistons came out without hassles. the 8th is driving me nuts!

I thought compressed air would nail it, but with my compressor at max pressure, the piston just moves forward slightly then then retracts when the air is off.

Only thing I can think of is piecing the caliper back together (refitting the 3 pistons I have already removed), reattach the line, re-bleeding and then try and clamp the 3 pistons that are free moving to force the 4th out.

But, before I go to all that hassle, I thought I wold check if anyone else has any other clever ideas?!

Thanks
Luke

[squirrel_hunter]

No other clever ideas, that is what I would do.

[barwel1992]

put some penetrating oil around the seal area (be prepaid to replace the seals) leave it for a bit, then get the air line on them when the piston moves back after you remove the line like you say it does it should drag some oil back past the seal with it repeat the process .

well it worked at my collage on a very old and rusty calliper

[andrewsmith]

Luke try a small pair of small molegrips and a small rag and try unscrewing it from the body.

Worked on an opposed two pot

[barwel1992]

Luke try a small pair of small molegrips and a small rag and try unscrewing it from the body.

Worked on an opposed two pot

please note it does not have to be a small rag ..... thank you come again ;)

[andrewsmith]

please note it does not have to be a small rag ..... thank you come again ;)

:smt097

Makes life easier and normally has to be chucked with the fluid that is stuck in the vacum behind

[barwel1992]

:smt097

Makes life easier and normally has to be chucked with the fluid that is stuck in the vacum behind

hehe

i know was just been a t*t :D

[andrewsmith]

I know!

Get back in the garage and break something! :mrgreen:

[barwel1992]

I know!

Get back in the garage and break something! :mrgreen:

i will be in a min the drill coming out and so is the broken exhaust bolt !

sorry for the derail

[husky03]

forget moleys mate-cut brush shaft to about 8 inches, shape end to fit tightly into piston, hammer in , turn and pull out at same time -take you minutes and you'll no screw piston

husky

[monkey]

Have you tried these Luke?

http://cdn5.mydeco.com/product_images/full/8a50255692576347ff45a6af71102ea5e223e77b.jpg

What bike is it on?

[yorkie_chris]

Some dangers of the err interesting advice so far.
If you muller the piston with mole grips, which is inevitable, you can also distort the piston out of round which clamps it in good and proper.
If you apply penetrating oil you may swell the seals and clamp it in tighter.

If you are going to attack it with mechanical tools, wind a jubilee clip around the offending piston.

Hydraulic method is best and safest way (preferably BEFORE you split system!). If you can seal the passageways in the caliper, you can replace one piston, fill it with water and then use a G clamp to force that one in, so popping the other out.

If you are going to use some caliper removal tool the expanding mandrel type ones are brilliant, the actual plier type ones are ok but haven't really got the balls behind them to pull a proper stuck one.

[suzukigt380paul]

put the other pistons back in,you may have to hold these in with a clamp or a vice and pump the stuck piston out with a grease gun,a air line will put out a 150psi, a grease gun about 10.000 psi and you cant compress grease so it has to move

[lukemillar]

Cheers for all the replies, I have a few things to try :)

[barwel1992]

If you apply penetrating oil you may swell the seals and clamp it in tighter.


worked on the race callipers that i was working on, although they had no dust seals so that could affect the way it worked

[yorkie_chris]

Not saying it will never work, just pointing out the risk of it.

[barwel1992]

Not saying it will never work, just pointing out the risk of it.

ohh right fair enough, the only thing we were told not to use is stuf like brake cleaner around the seals as they will blow them (yes you cant use brake cleaner on "brakes".... :???: can use it on every thing else though :p )