brake problems

[Fletchs90xj]

Hey there, I'm having issues with my brakes on my 90 XJ. I just swapped in a ford 9" with disc brakes and it had no pedal feel when the engine is running. The pedal will get hard with the engine off. It has always been this way since I got it. the shop that built and installed the axle is tring to figure out what is wrong with it before they give it back.
front calipers are about a year old
rear calipers are brand new
has 2 month old braided steel lines
2 month old master

they have tried a bigger bore Master and a new prop valve
tried adjusting the push rod off the booster aswell
all this done with no change
We are all pulling out our hair tring to figure this out and its getting expensive $$$$. Any help or Ideas would be awsome.
TIA Fletch
:huh: :huh:

 

[Abugarcia]

I would try a new master cylinder. I've heard of a lot of guys running Corvette, or E-350 master cylinders when swapping in rear discs.

 

[JeepinAudiophile]

if you decide to do this, try to keep in mind that doing a write-up on it would help a lot of people out.