blumax2007

I have a friend with a 641/2 with manual brakes. He is having trouble with the brakes. The more he uses them the more they will bind on there own till they heat up and close stopping the car. If he pulls over and lets the car rest the brakes release themselves and he can drive on. We have changed the master cylinder twice now??!! The problem still persists; does anyone out there know of a similar problem, and a cure?? Any help will be appreciated

kc5mhb

I have a 65 and 66 Coupe. The 66 belongs to my wife and I've had brake issues on it as well. The problem you are describing with not being able to stop well after use is brake fade. This happens after the shoes and drums heat up during use, a common problem for older cars. I remember seeing a show on how they used to test brake fade on older vehicles; they would get them atop a hill then ride the brakes all the way down. The heat also causes the brake fluid to get hot enough to start breaking down. My wife's 66 has a hard brake issue which you almost have to stand on the pedal to stop. I believe her car's issue is the distribution block (proportioning valve) mounted down below the master cylinder because I've replaced everything else. Anyway here is what I'd check and take this with a grain of salt as I'm no professional mechanic but I have old cars and have done much work on both of them.

Adjustment screws on the shoes too tight
Proportioning Valve
Wheel Cylinders sticking - improper installation of the springs and/or shoes
Kinked brake line somewhere on the car
Old brake fluid, trash in the lines - get a Mitey Vac tool and bleed them.
Master cylinder - Valve sticking (Its been replaced twice I see but I included this for others as a reference)

Unless your friend is planning on entering the car in Concourse events, I'd change out the master cylinder from the fruit bowl type to a split front/rear master cylinder like from a '67. I'm planning on doing that myself and there is some info out there on the swap. That way if you lose a wheel cylinder, you can still stop the car. Otherwise you'll just be pumping the brake fluid out the bad wheel cylinder and end up crashing. I've considered replacing the drums in the front with the disc conversion but not at the cost of replacing the wheels.

blumax2007

thanks for the info, I'll pass it along!!!