2000 Mercury Villager brake locked up

Lf brake locked up to the point of burning up pads I replaced both calipers and left brake hose still the Lf is not releasing when applied, all other wheels are fine I can open the bleeder and there will shoot out a stream of fluid(with a little pressure) and wheel will spin free but then when I apply the brakes it will not release unless I open the bleeder. There is a valve on master cylinder like a proportion valve and I can open the line there and it free's the Lf brake also, if I open the other line on back of m/c it stays locked. This car does have abs and the two m/c lines go into the abs pump valve( I assume) which transfers to all the wheels which are marked lf lr rr rf etc. I took of that proportion valve and it is very hard to blow through it but I assumed both front wheels would be locked if that was bad because it feeds the front brakes I assume Please help if you can. Ps I rechecked caliper and I can push it in by hand when off of car but I have to release air bleeder to push it in on car, it has pressure on it I can tell keeping it from going back in