need your help Asap plz! is my brake booster bad?

[dmac0923]

i tried posting in the tech section but my post didnt show up.
(01 sport)
i did a 4 wheel brake job and had to replace one rear caliper. bled the system with truck running properly several times. cant get a pedal. pedal is high and hard with the truck off. as soon as the engine is on, the pedal sinks right to the floor and the truck wants to stall

i tried it with the power booster plugged and the pedal seems normal. the vacuum hose from the manifold to the check valve looks good as new

is my booster bad?

 

[techieman33]

How does the truck idle? If it's a smooth idle then your booster is probably fine, but if it's running rough then you probably have a vacuum leak, and it sounds like you've probably narrowed that down to the booster.

 

[FordTony]

Also I would have bled the system with the vehicle off....not running ....thats how I've always done it. Also just for future brake jobs, I have always made out better replacing a pair of calipers at a time insted of just one......there pretty cheap rebuilt so its worth it..

 

[gijoecam]

Is the bleeder for the new caliper on the top or on the bottom? If it's on the bottom, they gave you the wrong caliper. (you need the other side).

Don't laugh. It's happened before on this board.

-Joe

 

[dmac0923]

the bleeder on the new caliper is on the top.

the truck has a very rough idle now. ive tried bleeding the ever living day lights out of the new caliper..

now with a test drive the vehicle only stops at the very end of the pedal travel

 

[Rottie]

Have you only bled the new caliper? If so try bleeding at all four corners.

 

[gijoecam]

How, exactly have you been bleeding it? With the engine off, have someone pump the pedal, then press and hold it, then crack the bleeder loose while they continue to press the pedal(the pedal should drop). Tell them to continue pressing it until you close the bleeder screw, then repeat. Do not let the reservoir go dry in the process.

The bottom line is that there's still an air bubble in there somewhere that needs to be purged.

Good luck!