azure76

I recently replaced my master cylinder, all calipers, all brake hoses, pads, rotors, and the brake lines that go into the caliper in the rear. I bled the whole system starting with the MC and found that i still had no pedal pressure. Rebled the entire system again and still nothing. Also, any pressure i did get would go away when car was running. Brake booster issue? Appreciate any help or info!

Peterbuilt

Did you bench bleed the new M/C?
The rear calipers have two bleeders, bleed the inners then the outers.
Power brakes use a 1&1/8" bore, non power brakes have a 1 inch bore.
Also some M/C have a deep piston hole and some are shallow, did you get the correct one?

azure76

I did not bench bleed the MC is that my screw up? I got an oem replacement for a 76 so it should be the right one. I did do both bleeders on the rear and from inside to out so i dont think thats my issue

J.D.78

bench bleeding MC is a MUST

0Willcox Corvette

Bench bleed the master cylinder as stated above... it is a must and the cylinder should have come with directions telling you how to do this. Think of it this way, the bore inside the cylinder is full of air and now you have pushed it into the lines.

Once you do this I would then find someone with a pressure bleeder and you'll solve your problem. Sometimes these old mules can be a beast to pedal bleed, but for us its a snap because we have a pressure bleeder.

We also tap each caliper with a brass hammer which will help you dislodge any air bubbles should one be trapped.

To test your booster, get in the car and apply slight foot pressure on the pedal, then start the car and see if the pedal moves downward with the same pressure. If the pedal drops the booster is working. Now this is not a sure fire way to test because you could still have a leaking diaphragm and pass this test.

IMHo
Willcox

azure76

Awesome thanks for the info! Ill be pulling the master cylinder to try a bench bleed and hopefully that does the trick after rebleeding the system. Ill also be trying the hammer on the caliper to be sure. I do have slight brake pressure now and when the car is running the pedal definitely goes in either so if i understood that correctly my brake booster is working.