Rear Disc brakes; caliper or further up the line
 

My daughter has owned this car about a year now. about 10 months ago a Front caliper let go so I replaced it and bleed all new fluid to all four corners.

She came home from college this weekend so it gave me a chance to look at the rear brakes which I have not done since she owned it.
I decided to change the pads just for giggles. After finding the one set of pads were rusted to the Rear bracket( not working at all) and on the other side one of the Float pins was rusted so it was not adjusting as the pads wore down.
OK got everything apart and cleaned and functioning smooth. The Caliper Piston moved in OK on both sides and I put it all together. After a short ride I came back home and it felt like the car was dragging. Jacked the rear up and aside front being HOT. I could barely rotate the rear tires. One side worse then the other. Would you suspect the calipers are a bit rusted internally and that's why they are dragging or is it common something in the proportioning valve or ABS is causing this drag?

I'd say its either the caliper or the flexible rubber lines to the rear calipers (there are three total). You can check the travel of the caliper by pushing the piston back into the caliper with the bleed screw open. If it goes back in somewhat smooth and with little resistance, I would doubt that is your problem. If the rubber line in the center that drops from the frame to the axle were to go bad, it could cause both rear calipers to lock up. It would basically act like a check valve holding pressure in the calipers even after you let off the pedal.

Sounds the same as mine. I say its the hoses. Replace all 5 if you can, including fronts. They are more than likely the same age.

It was the Calipers.
Replace and Bleed both rears and the car is happy now. The pads loosen up much much more now. After a drive to return the Cores, the rims were ice cold.
I probably wore down 4000 miles worth of brakes on the original test run I took.

New rule on this Blazer. Take the caliper off the bracket once a year and make sure all is functioning. I gooped up the Slide Pins and the Rubber boots pretty good to keep water out, I hope the previous owner just did a bad job and that's why the headache for me.