Just replaced all four rotors and pads on my 2000 GMC Jimmy SLE 4 X 4, ABS. Now the left rear brake is hanging and getting very hot. Can anyone tell me what would cause this? Do I need to bleed the system?

When you compressed the piston back into the caliper it probably didn't go in straight. Now the piston is crooked in the bore and is sticking causing the caliper to get hot. You can try to correct this if you still have the old brake pads. just replace the inside pad with an old one and pump the brakes a few times. Then remove the caliper again and leave the inside pad in the caliper to push against with the C-clamp and gently try to re-seat the piston. Never re-seat the piston without using something like an old pad. Don't use c-clamp against the piston directly. I hope this helps.

No try bleeding that one only if problem persists change cylinder/calliper
hope this helps?