Bad Master Cylinder or Air?

a few things come to mind.

1. you can not gravity bleed the rear drum brakes there is a valve in the MC that requires MC pressure to over come.
2. Have you adjusted the rear drum brakes to have a slight scrapping of the shoe on the drum as you rotate the drum?
3. air can get trapped in the lines and it can get aerated so there are tiny bubbles in the fluid that will take forever to get out.

If it was me I would get a helper and bleed the brakes from pass rear to drivers rear to pass front to drivers front. make sure the MC is full, have assistant SLOWLY depresses the pedal, if the assistant feels pressure you slowly open the bleeder, then close BEFORE the assistant takes foot off the pedal. ( tip... get some clear tubing that fits snugly over the nipple of the bleeder) if there is no pressure have assistant repeat lifting and pressing SLOWLY till there is pressure then you open the bleeder SLOWLY. This has ALWAYS worked for me

check the MC often if it gets empty you have to start over from the beginning.


Just a double check, you have a Disc Drum master cyl, the reservoir closer to the firewall is larger then the front AND you have your FRONT discs connected to it?