the donor vehicle never really ran and drove, so i dont know if the master cylinder was good to begin with, but the front brakes did work a little. after i bled the brakes (there was a lot of air in the front lines for some reason) i could get all 4 tires to lock up evenly when i hit the brakes, then the fronts gradually stopped working again.

would a bad seal on the plunger for the front brake circuit allow air into the system?
where would i get a 10 psi residual valve, and what exactly would it do?

thanks

-BrianM