Today coming home from work I noticed my brake pedal became hard and when I shifted to neutral it was VERY noticable that my brakes were still applied even though I didn't have my foot on the pedal. When I got in the driveway I checked the brakes and they were all hot. This has happened a few times before but I am having a hard time tracking it down. I am suspecting the distribution block, maybe the check valves are sticking. this has power drum brakes on it and I rebuilt the brakes about a year and a half ago. Any other ideas? Thanks!