1999 Chevy Blazer Rear Brakes Heat Up

I have a 1999 Blazer SUV with disc brakes on all four wheels. After about 15 minutes of driving I have noticed that both rear brake rotors are extremely hot, to the point wear water sizzles when sprayed on them. The front disks brakes do NOT heat up. I have removed the wheels and tried to eliminate the problem but everything seems to be working fine. The emergency brake pad is not touching the drum so it is not the source of the heat. I have taken the calipers off and have ensured they move freely when brakes are applied. It appears they are not releasing enough so constant pressure is on the rotor. I am at wits end on this. Do you have any suggestions? Thank you.