GMC Repair: 1995 GMC 1/2 ton 4 wheel drive truck brakes, flex hoses, slide bolts

Question
1995 GMC 4 wheel drive 350cu,5 speed manual transmission.When I drive my truck for a distance and stop a few times the front brakes fail to release. I've replaced pads, cleaned all touching metal parts, greased and cleaned the slide bolts, and cleaned the rotors.When they are locked up, if I bleed either of the calipers it releases both left and right side brakes so I'm thinking that it can't be the rubber flex hoses, right? If it was the hoses it would only release that side.The ABS light is on but I can't believe this system would ever hold pressure in the system or why it would do this. Please help with any information you can as I am at my wits end. When I have the calipers off and apply the brake pedal the pads travel inwards as they should and then release when I let off the pedal.Thanking you in advance, Phil

Answer
Hi
It MAY be the Master cylinder.
It MAY also be the proportioning valve.
I would check the valve first, then concentrate on the Master cyl.
I would also recommend at least having the codes read for the ABS, never hurts.
I Hope this helps.
Good Luck
Pawl