Rear caliper pistons

Robin Webster

Robin Webster

Hero member
Location
Silverstone
Ok, so thanks to Alan Bell I have a rear caliper for my 500.

Now wishing to refurb it the pistons will not budge. Tried pressure, tried penitrating fluid, tried mole grips, but it won't budge. 

Any suggestions over the piston removal before I break another caliper casting.

Robin.  (any1)
 
You've hooked it up to the master cylinder and tried to pump 'em out?
 
+1 for Reggies solution.

Have you a compessor? A zap with compressed air can work. Make sure to hold back the first piston that moves - to get the other one going. Don't be afraid to push them in to start the freeing process (assuming you have cleaned the exposed piston of course).
 
If you have dismantled it already you may want to try heat rather than try to rebuild and bleed it.
Try heat then molegrips alternately a few times, then liberally soak it in penetrating fluid.
I heard some folk just heat them up until the rubber seal gets destroyed but I would worry about distorting something in there.
 
Heat. Nothing will distort unless you keep heating well after the rubber has become soft as they are only held in by the seal.
 
Robin Webster said:
Any suggestions over the piston removal before I break another caliper casting.
Click to expand...
yea,  don't be in a hurry.  take ya time, lots of time.  and a bit of luck.  slowly worry the bugger out.
 
One of my more heavy handed cronies used to just dump anything that would not shift in diesel for a few days.
Claims it worked wonders and there was less chance of damaging it by keeping trying to work it.
 
Thanks gents..

Have tried pressure both hydraulic and air. Tried heat. Tried mole grips.  It sat in brake cleaner last night.

It's currently sitting in WD40.

Robin.  (dunno)
 
Robin Webster said:
Thanks gents..

Have tried pressure both hydraulic and air. Tried heat. Tried mole grips.  It sat in brake cleaner last night.

It's currently sitting in WD40.

Robin.  (dunno)
Click to expand...

Sounds like you could be heading for drilling/tapping the crown of the piston and then jacking it out with an m6 screw.  :-(
 
brake hydraulic system pressure before removing caliper or
using grease as the hydraulic when its off usually does the trick

if calipers are off and stuck i'll split them and put them in boiling water
when they are well and truly hot i can usually catch the dust seal lip of the piston
with a pair of screwdrivers and simply lever it out without trauma

good purchase with molegrips or similar to rotate the piston will help
before trying vertical movement of piston
 
And tonight LADIES AND GENTLEMEN

Tonight's STAR PRIZE GOES TO................

Can we have the Golden envelope Anthea?

Jotacorsa!

For the suggestion of boiling them in water..

If you wish to claim your prize of two used rusty Po5 caliper pistons please send a stamped addressed padded envelope.


Robin.  (bowdown) (clever)

 
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