Freeing up brake caliper pistons.

It's winter here so I'm performing some long put off maintenance on the 914.

Exhaust gaskets, valve adjustment and brakes.

I bought caliper rebuild kits but cannot remove one piston from each of the rear calipers. They've been soaking in PB Blaster for two weeks, nothing. I pushed compressed air into the system, nothing. I don't want to grab it with vise grips because I think they're cast iron.

Suggestions?

can you adapt a porta-power pump to the caliper inlet

Probably. Problem is that once one piston is out fluid, air or whatever doesn't push the stuck one.

How much heat can be applied before you get in trouble?

if I get what you're saying, the pump will run out of fluid?

Fill the caliper w/ hydraulic fluid (syringe) then hook up pump. Top off caliper if necessary.

The absolute easiest way to get stuck pistons out is to use a grease gun. I had to do it with the Cooper. Its super easy to control...No real POP. Trust me.

Leo

In reply to fasted58:

I think what he's saying is that there are two pistons in the caliper. One's already been removed, so it's no longer a closed system, so fluid would just come in from the pump and leave via the empty bore without pressing on the stuck piston.

Any combination of stuff you could stack in there to block the free piston in it's natural habitat while allowing room for the stuck one to move out?

I guess the same thing would be needed with Leo's tip, too...

In reply to nosleeves:

gotcha

I just gently place the old piston back over the hole, and just finesse the other piston out. The grease is a lot easier to clean up as well.

Leo

Put back the car's brake hose on it and press the pedal? As long as the other calipers are connected and in place you should be able to do it.

I would try pushing the piston farther IN, with a big C-clamp, figuring once you get it broken loose you can work on getting it OUT.

i agree with danny, and with whoever suggested clamping the free piston back in its hole so you can use psi to push the stuck one.

Easy, close the bleeder, plug the fluid port, fill the removed piston bore with brake fluid about 2/3 of the way, insert the free piston, apply C clamp.

The assumption here is you'll be replacing the pistons anyway so why not try (if all the above fails) to rotate the piston with large channellocks to free it up? Although I like Kenny's way the best. I'd be worried about getting the piston out if pushing it in fully doesn't do the trick.