I'm in the process of renewing the front brakes on my TJII wagon, as I only have the one car and I am kinda immobile without it I figured I would get a second set of callipers from a wrecker, pop new seals and boots in and lube as required, and basically do a complete swap-over with new pads and rotors too. Using compressed air to remove the pistons, managed to get one out (almost breaking my thumb when it released due to having it in a really dumb place... it's now the size of a small planet and hurts like a motherf&*ker!) but the other one is stuck. It came out about 7-8mm and stopped, had the pressure up to 80psi before I chickened out.

Question: Is there any other way to get the bloody piston out, preferably without hooking it up to the car, bleeding the system, and using the pedal?

Use a G clamp to push it back in, and try again with the air pressure.
Probably got a bit of rubber wear material or rust locking it up or the piston is cock eyed. Too much pressure will/may fracture the caliper if it is cockeyed.

HINT: Thumb, no. Block of wood yes! <--- recommended way of popping out the piston with air and stopping it from clunking into the caliper bits.

If it still sticks, run some brake fluid into it, then work the piston in and out with the clamp and air pressure. It will eventually pop, hopefully, maybe, possibly.
If utterly hopeless, take it back and ask for another.

Cheers Max, I'll give that a go... once I have use of all my appendages again!

Just to follow up on this so the thread can be closed with a result, your method did the trick Max. Ran the piston back in with a G clamp, squirted a bit more fluid in, second attempt with the air and it popped out good-o at only about 10psi (thumb WELL out of the way!). Job done: callipers reco-ed (cleaned, re-greased, new rubbers/o-rings), discs replaced with new, new pads, lines bled. Car stops nice and quick with no vibration so I no longer have to look for Fords going slower than me (don't they all) to lunge into the back of and use as a form of impromptu anchor! (Just kidding, I generally looked for Subarus).

Good one!
Did you find any grot or rust in the calipers? I've been meaning to pick up a pair to recon, must get around to it.
How much and where did you pick up the rebuild bits?

Can't remember the $ on the kits, I've had them for over a year but from memory not much, under $20 each I think (they only contain the O-ring, main boot, and the guide pin boots). Got them from ABS if I recall correctly. The callipers I got from Pick-A-Part for (I think) about $25 each, they were fairly grotty outside but cleaned up ok. They weren't too bad inside, a bit of gunge in the back of the cylinder but overall pretty tidy (I could have reco-ed the callipers I had but wanted a straight swap over in case of problems). There were some small rust spots and marks that looked like something caked on, a light massage with a soft (brass) wire brush brought them up like bought ones. The main boots were fiddly little f%&kers to get in place but otherwise no probs. I was concerned the discs would be a bugger to remove but no problems, driver's side needed a bit of gentle convincing with a rubber mallet but the other just lifted off. Tidied up the hubs with a wire brush before fitting the new discs and wheels and torqueing up to specs.

From memory $25 sounds right.
Madmax's method is the way to go.

kits . . . . under $20 each . . . . . . Got them from ABS if I recall correctly.

The callipers I got from Pick-A-Part for (I think) about $25 each


Thanks for those facts!