Chevrolet Repair: locking brakes; 2005 chevy express 2500, caliper pistons, brake hoses

Question
Put new pads front & rear. Next day brakes got stiffer with driving to point of locking up. Hydroboost was suggested as problem. Replaced that; seemed to be good. Later, locked up again. Raised truck up & verified front wheels locked. Separated master cylinder from booster & wheels freed up. Reattached & all OK. Went on half hour test drive; all OK. Let truck sit 2-3 hours, test drove again, problem returned. Used new a/c delco part. What am I missing?

Answer
Hi Mike....if your brakes didn't do that before you replaced the pads and shoes then i wouldn't think that the boost is the problem, but check this...when you replaced the boost did it come with a new push rod...if it did is it the same length as the old one...if it didn't check to see if the depth of the hole that the push rod goes in is the same depth as the old booster.if everything is the same as the org one then booster is not the problem...check the front brake hoses, i have seen where they will collaspe inside and hold the brakes on, did you check calipers and sliders and make sure they are not binding and that caliper pistons went back in freely when you put new pads on. measure rotors if they are too thin you could have calipers travelling too far and hanging up...they should be no more than 60 thousand less than new spec....i would be leaning toward the brake hoses...Hope this helps