My 1983 f250 6.9 has some braking problems have instaled new vacum booster and mastercylinder, pads and shoes are excellent no leaks in slaves or calipers, pedale is mushy slow to stop, vacum pump has only 8 lb pressure at idl. and 11 lb at high rpm no leaks pressure holds steady even with engine off, but drops when brakes pedale is pushed. I need to know how much pressure is the pump suppose to have at ide and high rpm do I need a new one.

 

I WOULD LIKE TO KNOW ALSO AS I'VE REPLACED MY MASTER CYLINDER 6 TIMES AND MY BRAKE PEDAL STILL CREEPS DOWN WHEN SETTING WITH BRAKE PEDAL DEPRESSED OH YES THE LAST TWO MASTER CYLINDERS WERE NEW NOT REMANUFACTURED

 

david paul and anyone else with vacum boost brake problems, check your vacum pump inch level with a vacum gauge, my old one registered 8 inchs at idle and 12 and higher rpm, my new one showed 29 inchs at idle and my brake light went out as soon as it started brakes now work fine. What a difference, if you have already done everything else try that, if you develop brake problems and have no fluid leeks check your vacum pump with a vacum gauge it has to have a high reading if you don't have a gauge get one it is a lot cheeper then doing it the hard way as I did. good luck.