I have a 1967 Chevrolet Camaro with manual drum brakes on all 4 wheels. Standard transmission with 250 cu in 6 cylinder engine. Approximately 101200 miles. Problem: Brake pedal goes next to floor before getting some braking action on rears and no action on the fronts. Have replaced the master cylinder several times with different well known auto supply store new units. New lines. New brake wheel cylinders installed several times on all wheels. New brake pipe distribution block/switch assembly (brake safety switch is located in this block). Bled the master on each installation. Lines bled good and confirmed with Monroe store that they were free of air and who just scratched there heads on this one. New shoes (up-grades to Bendix). Have double checked the clevis pin location to make sure it is in the right hole in the pedal assembly. Have checked several times to make sure the rod is seated in the deep socket master cylinder and that I have 1/16 to 1/4 inch free play as the spec call for. Dash brake light is on indicating there is a pressure imbalance in the system but I can't find it.
Check the combination valve that activates the light-its been long long time-If I can recall you have to open it while bleeding. Or apply excessive force on the brake pedal to reset the light.
October, 28, 2007 AT 7:22 PM
If by " combination valve" you are referring to the brake distribution/switch, I have bled it by running lines back to the master. Excessive force as been applied by pushing the pedal to the floor. No change in condition.
October, 29, 2007 AT 5:16 PM
There is still no front braking action with the front shoes.
October, 29, 2007 AT 7:05 PM
Open up the front brakes and investigate, everything okay there-Its time to put the Master Cylinder on the operating table-its got a primary and secondary section to it-find out what' happening with it. Could be it all along. Make sure the cup are facing the right way. Been there facing the other way-no pressure.
October, 29, 2007 AT 9:18 PM
As indicated in the first post, the front wheel cylinders, hardware, and shoes are all new. The shoes are free to move but there does not seem to be enough pressure to move them out. There is plenty of fluid getting to the wheel cylinders though. The master has been replaced several times with different manufactures and each has pushed ample fluid to the cylinders to move the shoes but they don't. This is the most confounding problem that I have run across in 40 years. What are the odds of several different new masters having the cup facing the wrong way?