Stuck brake piston....

[Seana23]

Hej da. Ive got a GS with a stuck brake piston....
How do i get it out???
Air line, mole grips, large hammer!!?
Ive soaked it in WD40 but its still stuck...
What can i try now?

Thanx all.
Seana
XXX

[Nessism]

Air line works well. The piston may shoot out when it releases so protect it with a rag, and keep your fingers clear.

[scaylabs]

I had a really stuck one and had to use a combination of everything above: PB Blaster (penetrating oil, better than wd-40; thank you GSR!), air line into the caliper with one hand, holding the caliper down to the bench with the other (clamps were not enough) AND a buddy with vise grips pulling on the piston!!

Hopefully yours will be easier, just keep going at it!

[rustybronco]

If all else fails, thread a bolt in the banjo bolt hole of the caliper, loosen the bleeder screw, put the end of a grease gun on the alemite fitting and pump away.

if you don't have a grease gun, pack the banjo bolt hole with grease and thread a bolt into the hole-repeating as necessary.

[Octain]

Is there enough of the piston to grab with a bench vise?
If so you'll get much more leverage to pull and twist at the same time.

[pete]

I tried air, no go, ended up with a pipe wrench on it.

Be warned if you do that it will be unusable afterwards, and check your cylinder bore very closely!

Actually... is this the brake caliper piston or the master cylinder piston?

[Digitus]

I always reconnect the original brake lever, bleed the system roughly using a vacuum pump and just work the piston out by using the brake lever. Always works. in case of multiple pistons, you'll have to think of a way to stop the other piston(s) moving too far out.
Once all the pistons have a mm or so left, you can usually wiggle them out by hand.

Be very very careful with air pressure. I saw someone try that, he shot the piston through the roof and never found it back

[Seana23]

Excelent, thanx all. I dont want to write off the piston (brake caliper piston by the way) so ill try the Penetrating fluid first and work up to mashing it up.
Thanx again, ill let you know what eventually works...


Seana
XXX

[chef1366]

Put an o-ring between the air and where the line bolts in. Push down hard. Mine popped out.

[Seana23]

Good news Peeps. They came out!! Using the Ole Screwdriver and Angle grinder Spanner Lever trick... One either side under the lip ov the piston and plenty ov WD40, and..... Pop! Out they came.
Thanx for your kind advise.

XXX

[pete]

Glad to hear you got it out! Now the fun part to inspect that cylinder bore and make sure she's all hunky dory for a newey...

[Seana23]

ok, ive cleaned it up and oiled the seals... is there a knack to getting the pistons back in straight, so they dont wedge into the cylinder? thought maybe a vice that gives an even pressure when pushing it back in??? any other way?

Seana
XXX

[mike_of_bbg]

I just pushed mine in. It shouldn't take too much pressure.

Have you seen this caliper rebuild tutorial on BassCliff's site?

http://members.dslextreme.com/users/storagecliff1/images/brake_caliper_overhaul.pdf

[Rover]

Coat them with some brake fluid,a little lubrication may help.

[rustybronco]

Put a little bit of air pressure into the banjo bolt hole and place the brake fluid lubricated piston squarely over the dust boot. air pressure will cause the dust boot to go around the caliper piston allowing you push the caliper piston easily with your hand into it's bore (after removing the air pressure from the port) .