power brake issuses

[71broncrollsport]

i have a 71 with a 302 c4 and i did the chevy disc brake conversion and rebuilt the rear drums. i installed master power brakes power brake booster and have bled the the system. when i hit the brake i have very little stopping power not engough to hol the truck from moving. i do not feel the booster assisting at all. when i push the brake to the floor it retuns slowly any ideas on the problem? im pretty sure its bled right so maybe the linkage?

 

[Bully Bob]

Hmmmmm.,

A bit un-clear to me (maybe someone else gets it) but., you make no mention of the "master cylinder"

Is it orig. or new...? Same for the booster, new or original..? What brand are they ?

MEANING.., did you have a power brake set-up prior to mods., or are these add-ons.?

---AND---

"when i push the brake to the floor"

Really..? Is the brake pedal actually going clear to the floor...?

 

[S_bolt19]

Are all your vacuum lines hooked up and hooked up correctly?

 

[71broncrollsport]

i have put on new brakes all around disc in the front and rebuilt rear drums. i installed master power brakes disc/ drum master with booster and braket. i also added there combination valve. and when i said push the brake to the floor i mean fully depress it, it does not hit the floor. the only parts i have not replaced are the rear hard line axle lines and frame to axle hoses but i have new ones on the way.

 

[Bully Bob]

Still un-clear...,

What I'm gett'n at is did you put back on the orig. M/C or buy a new one...??

If you let the orig. one drain.., or put on a "NEW" one...you likely have an air bubble inside the M/C

Meaning..., did you "bench-bleed" the M/C..?

 

[71broncrollsport]

i installed a whole power brake kit that includes a new master, booster and bracket. i did bench blead the master but i did it with it on the booster and braket installed in the bronco so i was pushing the pedal to bleed it. i suspect the booster because of the odd slow returning pedal while the engine is running with the vacuum hooked up, i do not get this slow returning pedal when the engine is off.

 

[Bully Bob]

Who was the supplier..., one of our EB stores..??

I think contacting them would be in order.

You didn't say but the pedal shouldn't move more than an inch or two.

Also., as with most, (eng.off) the pedal should restrict depression after a few pumps. :huh: