I had serveral times of terrible experence about stick rear caliper .

                     and it is always happen after about 10 minutes running on highway , the 'giiiii' sound generate from rear
                     wheel ,I try to push the brake and sound gone , but once release brake it happen again , continuous
                     'giii'.....

                     then I went to interchange and stop car . the right hand rear brake generate a lot of smoke and heat ,
                     even the wheel get very hot while I touch it .

                     I try to push the brake very heavy for several times , and start to go to highway , the 'giii' sound gone .

                     I think that must be the rear caliper stick on the disc and can't release itself .

                     What can I do ? lubricating the piston of caliper ? or .....

                     .................or replace the caliper.

                     Odds are that now your rotor for that wheel is also blue and warped too (replace) with new pads.

                     Warren,

                     I've had the same thing happen to me twice with the left rear brake caliper. Once about 2 years ago, it
                     seized up and required replacement, and then it did the exact same thing last week, taking the rotor and
                     some other parts with it to the tune of $630. Same exact problem.

                     All other calipers on my car, with 115K miles, are original. Something about the left rear in my car
                     seems prone to failure (sigh). Unfortunately, none of the mechanics have any idea why it would be just
                     that caliper to fail.

                     --
                     Mark B. '94 850 Turbo w/ upgraded turbo, ecm, exhaust & suspension

                     my left rear caliper piston first began to stick at around 170,000 miles. I was able to "free" it up by
                     taking the brake pad out on the sticking side and then prying hard with a crow-bar using the disc as a
                     lever point. Not a very elegant solution, but if you take care to protect the disc surface (thin pice of sheet
                     metal) you can actually get pretty good leverage and sometimes succesfully free the piston. Be sure to
                     keep the pad on the non-sticking side so that you don't force the disc too hard. I repeated this cycle 4-5
                     times, each time I retract the piston, I'd step on the brake and get it to come out again, then
                     retract...you get the picture. This worked 'till about 200,000 miles when I noticed it seized up again. I
                     freed it up again but will now go shopping for a new caliper as the old one has served me well enough
                     with 210,000 miles. I don't think they're terribly expensive.