I have a 1989 Ford Thunderbird. The brake pedal comes all the way up and the front brakes lock up.

This occurs when simply driving down the road at 55mph without even applying the brakes. It seems to be a vacuum issue rather than mechanical. I had new rotors and pads put on 2000miles ago and again 500 miles ago, thought that was the issue it was not. When they lock up you can feel it in the wheel wobble and actually see the temp rise and the front tires and wheels get smoking hot. It this in the master cylinder or vacuum related? Any ideas? Appreciate any help.