hey all new poster here hope someone can help me out. i have a 99 2500 4x4 5.9 gas . finished puting the front axle back together after hanging seals. took it for a test drive and lost brakesafter about 10mi pedal just went to the floor! cant find any fluid leeks and fluid level looks good. with the truck off i can push the pedal and get brakes (pedal gets hard can here the calipers moving) as soon as i start the truck goes right back to the floor. first thought was the booster or master but wheen i look on the web i see al sorts of pepole having problomes with abs controler and dont have a lot of money right now to throw parts at the probloem. THANKS

 

Any lights in the dash on? Here any odd noises when you step on the brakes? (engine running.) Will the brakes pump up? (pump the pedal several times)

Welcome to DF!

 

nope when runing cant pump it up truck off yes. the brake light is on but has been on(broken e-brake handle) didnt notice any noises.

 

bleed the lines! sounds like an air pocket in the lines....

 

plan on it just waiteing for my dad to get home so i can get my vacume bleeder out of his shop all i have here is pressure bleeder

 

Probably the vacuum booster.

 

tryed bleeding it no change. does anyone know if you should be able to pull a vacume on the boster? tryed with a vacume pump and cant get above 2pds of vacume

 

Do you get 'boost' when you step on the brakes with the engine running? When you shut the engine off, is the pedal immediately hard to push?

 

not sure what you mean by boost? if i have my foot on the pedal pushing when i start it it setels to the floor. when i shut it back of i pump it once and it gets progresivley harder and cant make it to the floor then hard at the top when you relese the pedal and try to push it back down.

 

if you have a firm brake pedal when truck is not running,
and then completely lose the pedal when the truck is cranked, i'd suspect the booster.

this is a question- is there any way to prove it by disconnecting and bypassing the booster vac line ? you'd not have power assist brakes, so be careful.