Compressed air must be used with GREAT caution. Works great with a dust blower tip held lightly on the brake line hole so that you don't get much pressure in there when the pistons aren't stuck.

If they don't come out with light air pressure, you are better off to put the caliper back on, clamp the good piston down with a C-clamp, and use the brake pedal to force the piston out. Brake fluid doesn't compress, so when the piston finally pops loose, it will only move a short distance. Compressed air, at 100 psi or so, will expand explosively, and the piston can bounce off the caliper and kill you if it hits you in the head.

If you MUST use compressed air to force a stucl piston out, put a soft board in the caliper so that the piston will hit it before coming out, and KEEP HANDS AWAY. Keep the caliper pointed open end down so that the piston, if it flys, will hit the floor inside the caliper.

I usually just use two screwdrivers or small prybars and work the piston back and forth to get it loose. They are most often stuck from the backing plate hitting the antirattle spring, so a tap or two on the top of the piston will straighten it out in the bore so it comes right out. I have battled one for an hour or so (on the 280), turned out to have a rusty bore above the seal.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!