I replaced the brakes on my '71 SS (front disc, back drum) and attempted to bleed the brakes. No luck. Needed a new master cylinder, so got that. After I bled the brakes again, I had a really nice amount of pedal to press. Whenever I started the engine, though, the pedal easily went to the floor. I've gone through a few other master cylinders and gotten the same results. Could the vacuum on the power booster be bad, causing this symptom, or is there something else I should be aware of? Thank you.

Originally posted by soccerguy045:
After I bled the brakes again, I had a really nice amount of pedal to press. Whenever I started the engine, though, the pedal easily went to the floor. I've gone through a few other master cylinders and gotten the same results. Could the vacuum on the power booster be bad, causing this symptom, or is there something else I should be aware of? Pedal going to the floor is usually a sign of a bad MC. Even though you don't see signs of brake fluid leaking, it could still be (e.g. leaking into the booster). You said you replaced your brakes. Did you make sure the bleeder on the calipers is facing up? Any other leaks around the wheel cylinders/calipers?

It may take a few MC's before you find one that actually works. I think the quality of the MC rebuilds has suffered quite a bit over the years.

Joe