No power brakes

[1969_Mach1]

How strong is the vacuum signal to the booster, if it's less than about 14" the power assist starts to suffer.  12" of vacuum to the booster is really the minimum for any type of power assist.  If the vacuum signal is okay, I'd think you have a bad booster.  Where did your mechanic get the new booster?

Just to clarify, the brakes will work, just the pedal force needs to be extremely high?  Asking, because if the won't work at all regardless of how much you push on the pedal, there is a chance something hydraulic is plugged somewhere.  But, if something is plugged, you should still feel some power assist.

One test I have heard of is with the engine off press the pedal several times to eliminate any residual vacuum inside the booster.  Then, while very lightly touching the brake pedal start the engine.  If the booster is working you should feel the brake pedal pull down a little bit.

Thanks. I will double check the vacuum pressure but I think it’s going. I’ll also try that test. As far as the brakes working! They barely do. Put my full weight on the peddle as far as it goes down. I can feel the brake making contact with pads but it like there not applying any pressure to the pads. Feels like they are just touching or rubbing against them.  Does this do much good.

With the car on jackstands have you tried having one person manually rotate a tire and another apply the brakes?  Just trying to determine if something is plugged, but, since you mentioned in your first post they were bled extensively it's starting to look there is no power assist.


Is the pedal going nearly to the floor?  First, if there is no air in the system and the master cylinder is leaking internally the pedal with go nearly to the floor and the brakes will not work.  Second, rear brakes far out of adjustment will cause the pedal to travel too far and the brakes will work but not as well as they should.