Classic/Antique Car Repair: 48 pontiac brakes, wheel cylinders, slave cylinders

Question
hi brad,  i have a baffling problem with my 48 pontiac.  its stock .  last summer i rebuilt the master cylinder, rebuilt the slave cylinders and put new brake shoes on the front. now when i drive the car i can go about 20 miles and the brakes keep getting tighter and eventually they get so tight the car comes to a stop. then i have to let it sit for awhile and wait for them to cool before i can move.  it effects all 4 wheels. i am sure i have the brakes adjusted properly. it happens even when i use the brakes hardly at all, going uphill, ect. what did i do wrong?  thank you for your time....gary

Answer
The first thing that I would check on this car would be the adjustment of the master cylinder push rod. To check this push on the brake pedal with your hand, not your foot. The first 1 inch of pedal travel is what we call free play. At about 1 inch of travel you should be able to feel the master cylinder push rod touch the master cylinder piston and the resistance pushing the pedal further down should increase. If this is not right then the master cylinder piston is not releasing fully and the compensating port in the cylinder is not allowing the fluid to return from the wheel cylinders. If this is ok then I would suspect a problem in the master cylinder like the ports in the floor of the fluid chamber could be plugged or restricted. The above is if all 4 wheels are locking up. If it is just one wheel or the rears only the problem could be one of the hydraulic is disintegrating internally. These are the most common cause.