I need help to diagnose my brake problem.My booster makes noise when the brakes are applied.the brakes feel fine until the pedal is pushed far toward the floor,then is gets hard to push and front brakes dont lock up.I know I dont have quite as much vacuum as I probably need(10 inches at idle).when I have brakes applied fully at idle,the vacuum goes down 2 inches.I dont want to spend $300+ for a vacuum pump if its just a ruptured diaphram.Is the noise coming out of the thing the smoking gun?Has anyone had a ruptured brake diaphram before?It was a new one 2 years ago from MP brakes.Brakes never did work all that good.Everything replaced from that kit except the vacuum box.

 

Odds are good you have a torn diaphragm.

 

And/or you have air in the front brakes....

imo you should be able to lock the brakes even without power.