Front brakes seizing

Vehicle: 1990 Izuzu Pickup 2.3L 2WD 155000 miles.

Problem: Both front brakes are seizing. Not so hard you can’t drive the vehicle but hard enough it is difficult to turn the wheels by hand when the truck is lifted. Driving the vehicle for distance causes the engine to run hotter than usual due to the stress the brake drag is putting on the engine.

So far; Replaced both rotors, new brake pads, new calipers, inner and outer wheel bearings, master cylinder, proportional valve and flexible brake lines to calipers. Used synthetic lube for caliper slide pins.

Bled system plenty of fluid coming out bleeder valves at good pressure rate.

My problem is still occurring; I then removed the two metal lines from the master cylinder to the proportional valve and ran a wire through both and high pressure air to make sure no blockage preventing fluid from returning to the master cylinder. Also did the same to to drivers side metal brake line. Still same problem the brakes are seizing. If I open a bleeder valve and release pressure and retighten the valve the wheels spin easily until you brake with the pedal. Also, disconnected front brake lines off the proportional valve, same thing, wheels spin freely/easily and once pressure is reestablished same problem.

Does anyone have any ideas? I don’t know what else there is to replace. The system acts like the fluid is not returning to the master cylinder but I don’t know what else to do.

Questions for you:

Does the brake pedal return all the way to the top of its travel when you release it?

What happens if you pull the vacuum hose off of the brake booster (car not running) and press the brakes? Do they seize then?

If yes to the first one, and no to the second, I have not much else for you. If no to the first one, is there a pedal return spring on this vehicle? If no to the second, suspect the brake vacuum booster.

Yes the brake pedal returns all the way to the top of travel.
Disconnected the vacuum line off the power booster-same problem with them seizing.

di you check the rod under the dash.the rod from the pedal into the master might need turned in. if it is too long the master cylinder wil not return all the way holding the brake on

That was my thought too

Tried your suggestion this morning. Moved the play on the brake rod in and the wheels are now spinning freely. THANKS SO MUCH! Marco