97 no brakes while running

[BigRedJeep]

Brakes seem firm while truck is off, as soon as started firm pedal, slowly goes to floor.

replaceed, rear brakes & drums, brake line, ebrake cable. rotors, pads, master cylinderx2 not loosing fluid. this is my friends truck, been in the shop all week

help!!!!

 

[hheynow]

Bad vacuum pump?
Hook a vacuum gauge to the hose that attaches to brake booster.
It's a 3/8" ID hose.
Start the truck, pump brakes, shut off and read gauge.
If you see a low vacuum reading say <10", the pump is bad.
A new vacuum pump pulls between 20-25 inches.

 

[BigRedJeep]

just replaced vacume pump with a $100 unit from o'rileys sill does the same thing, rears lock up in graval but not the front. pedal is still the same goes to the floor slowly.

he is sapose to take the truck and pull a 2 jeep trailer to go wheeling today for a big run this weekend..

 

[BigRedJeep]

i think its fixed... we will see in the coming weekend. thanks heynow for your help i think the pump fixed most of it