Quote Originally Posted by hottrodd57 View Post
That why I'm thinking, no proportion valve, just brass tee's. When I dis connect the Booster, I couldn't even press the pedal down. But how can the booster be over assisting? I don't know what else to check/ or replace. Notalot the brake sys on car
There is a valve inside the booster and that is failing \ has failed. I had one in my Mustang do that. Was a B_ _ ch to drive with that problem! I removed and sent it out for a rebuild to a reputable shop but it failed again soon after So I bought a new one. I don't know what else fits a Bonneville but I think any good parts store should be able to help.