Random brake pressure loss, but only for a moment

[airfire4]

As the title states, I randomly lose brake pressure when climbing obstacles or when the front of the jeep is pointed up. It was a issue when got my build done and took it out for the first time and was maneuvering around some trees while pointed up hill, and it stopped fine the first time but when I went to stop after reversing I had lost all brake pressure. I quickly pumped them and they came back while pointed up hill, and it continued to do it randomly that day. I did stop to inspect for any leaks or kinked lines and everything looked fine and there was no fluid loss.

Fast forward to a few months ago i went through and bleed everything, the MC, prop valve and all four corners again and the pedal felt great after that and stopped better to. So last night I was bleeding the air out of my power steering with the front wheels off the ground for like 30 min or so, and when I put it back on the ground and backed it into its spot, there was no brake pressure once again and had to pump it to get it back and it was fine again.

Now around town and in normal driving conditions i dont have a problem at all. Im kinda lost on what to do now other the replace the MC and the booster, some have said that something may have gone wrong in one of those. Anyone have any thoughts on what could be going on here??


2001 XJ
Factory master cylinder
Factory brake booster
Factory prop valve
Factory brake lines on the body going front to back
New extended braided lines on the front and rear
New calipers on the D30 front
New calipers on the 8.8 rear
New hard lines on the rear axle and new hard lines going to the front corners

 

[tech1001]

I would check the front braided lines and see if they are any bends that are to tight and when were they changed ?before or after the lift.

 

[airfire4]

They were put on during the lift install. They’re what ever iron rock uses with their lifts. I do have a nice set of crown extended lines that I haven’t put on yet, the one for the rear is already on since the rear line from iron rock failed shortly after install. There no hard bends or kinks in those front lines, just nice easy curves

 

[RCP Phx]

I would be the brakes again with the MC level, you might need a pretty steep downhill to achieve this!