Had this happen to me as well. The rod between the master cylinder & the pedal is too long, so the brakes are dragging & overheating. Try to shorten this, some Master Cylinders have a thread & a lock nut. Or you could try swapping the rod from the old master cylinder. Or adjust the pedal stop so the pedal comes out a little. You could also slip some of those 'half moon' spacers between the master cylinder & the firewall. They are usually hard to find after putting them down, like pens or markers. If none of this is the case, it could be they have given you a brake drum master cylinder, which has a residual pressure valve, which will keep pressure in the front circuit.