rear disc getting hot

? can you re-write the post? is the rotor hot? or just loose? whats disc?

It is normal for the pads to drag a little especially when new. But under normal conditions the disc should not get so hot you can't touch it. Sometimes when pads are changed and the pistons are pushed back into the calipers gunk gets trapped and causes the pistons to stick. When you put in new pads (front or rear) it is a good idea to extend the pistons a little and scrub out the caliper with brake cleaner before pushing them back in.

well the brake is still draging so i took the caliper apart and clean i and clean the piston .and it still drags.the brake pedal feels funny and is hard to stop and no air is in the line.so im going to replace the rear mastercylinder

Did you give the new pads time to bed in? It takes a while, and quite a few stops to get them properly bedded in.

Oh yeah, if you use your rear brakes, the rotor WILL get hot, just like how the front ones get hot when you use them.

Just squish down harder on that brake pedal a couple times until they bed in properly.

BC.