Yea, connect it back to the system, put it over the rotor with no pads in it and STOMP on the brake pedal. This only works with otherwise sealed systems. If there is lots of air already in there you might actually have to bleed the system again just to get this to work, but when all else fails, this will work. HTH.
The easiest way that I know to get a stuck pisto out of a brake caliper is to reasemble all the other pistons into the caliper. Insert an apropriate sized block of HARD wood between the two pistons that are fre and use a large G cramp to hold in the third piston that is not stuck. Hold the caliper in the vice.
Get a flexible hose for your grease gun and remove the chuck from the end. The thread (at least on mine) is the same as the thread for the hose fitting on the caliper. Fit the hose to the caliper and the grease gun. Start pumping. This will fill the caliper with grease and pop the stuck piston out of there.
BEWARE: The stuck piston may escape with some considerbe force and scare the crap out of you. I generaly cover the whole mess with a rag after checking that all is working as desired and the clamp is holding the opposite piston in place.
After this I generaly split the caliper in half ( I know what they say in the book. Be careful not to loose the O rings) to clean all the grease out and then run a small hone through into the bore of the caliper. You will notice that al the corrosion is on the caliper area outside the seal. Honing this off will prevent the caliper from sticking as soon as you reassemble it.
Make sure it is all spotless when you reassemble the caliper.
Just freed one of the front d/s pistons last night.
Jack up your unit.
Turn your wheel for easy access.
Remove the wire, two pins and thin plate.
Now you may have to clamp your pad/pads in order to remove them or if lucky they will just slide out.
Once the brake pad is out slide a thinner than pad chunk of wood where the pad was, start the truck and push on the brake pedal.
This will force the piston out allowing you to clean the outer surface which more than likely has been corroded.
Make sure you apply even pressure to the piston when clamping as little suckers can bind, a fat socket inside the piston can help otherwise keep moving your clamp side to side.
While you are at it check the other pistons, I shoot a little white grease into all of the rubber boots by lifting the boots and inserting the plastic tube from an aerosol can.
yeah, just spent hours trying to get my piston aloose, but here's what finally worked, open the fluid valve on the caliper and leave open, if a clamp doesn't work take a hammer and hit the piston on the top, bottom, and sides being careful not to hit to hard, only enough to see it shift at different angles, once this is done tap it until it is straightend back out if it shifted any and start hitting at the dead center of it, keep hitting, it should start to go in after a couple of hits, if not keep hitting, good luck