brake problem

[demoncar71]

i have a 1956 plymouth belvedere, here is my problem, has new shoes,wheel
cylinders,hoses and master cylinder. the wheels lock up after driving awhile, i can open a line at m/c and relieve pressure. i have put a new mc and 2 reman m/c's on still same problem. any ideas?

 

[340sixpack]

The pushrod on the back of your master,is it adjustable?Not a brake expert by
any means but had this happen to two of our cars,shorten the rod and they were ok.I had an adjustable on mine so it was easy.The other was a reman
like yours came with the rod in m/c already,obviously the wrong rod for
application.Check your piston in the m/c after pressure is relieved and see if it is sitting back in the bore all the way,I think the problem was the piston was not back all the way and when you drove it it would build pressure putting the piston all the way back but the pedal would bottom out on the
brake switch leaving pressure on the m/c and engaging the brakes.I hope this
makes sense easier to do than explain.

 

[340sixpack]

Also check your brake switch bracket,if its adjustable try moving it forward
farther.