Ive bled my brake lines on my 79 Z and all that work are my rear drum brakes. I have to burry the brake pedal when I stop and it sucks!! I replaced the master cylinder about a month ago. I also replaced my front calipers about a year ago. I have pressure in the lines because I was able to bleed them all... including the bleeds on the master cylinder. Whats up with my brakes?? Is it the booster that might be bad? Thanks!

 

did you bench bleed the master cylinder befor you installed it and how did you bleed the system it sounds like air in the master cylinder to me or your rear brakes are out of adjustment