Braking system

[Mudboyzjeep92]

Hello everyone I’m new to this group I have a 90 MJ and I’m having brake issues my issue started with the pedal just going all the way to the floor. I bled the brakes and worked a little bit and went back to doing the same thing I have recently yesterday changed the brake booster, and the master cylinder played all the air out of the entire system and my brake pedal is still spongy and goes to the floor only thing I haven’t changed is the proportioning valve all this started a few years back when I took it off Road and ripped the rear brake lines out of the axle and it’s been trouble ever since so sadly I haven’t parked and really don’t drive it does anybody know what it maybe 

[ghetdjc320]

Do you still have the rear load sensing valve? When you replaced your master, did you bench bleed it before install? 

[fiatslug87]

Did you follow the MJ specific brake bleeding procedure?

 

In order to bleed MJ brakes:

Open the right front bleeder

Depress brake pedal and hold

Start engine, brake light should stay on after engine starts indicating bypass valve has moved (sensed front brake leak)

Turn off engine, leave bleeder open, release parking brake

Bleed left rear 

Bleed right rear

Bleed righ front (close bleeder when done)

Bleed left front

then repeat bleeding with right caliper closed

 

from the ‘92 service manual

[ghetdjc320]

2 hours ago, fiatslug87 said:

Did you follow the MJ specific brake bleeding procedure?

 

In order to bleed MJ brakes:

Open the right front bleeder

Depress brake pedal and hold

Start engine, brake light should stay on after engine starts indicating bypass valve has moved (sensed front brake leak)

Turn off engine, leave bleeder open, release parking brake

Bleed left rear 

Bleed right rear

Bleed righ front (close bleeder when done)

Bleed left front

then repeat bleeding with right caliper closed

 

from the ‘92 service manual

 

But before you start, make sure you completely bleed out your new master cylinder 

[cruiser54]

And make sure your rear brake shoes are adjusted properly. 

[Mudboyzjeep92]

19 hours ago, ghetdjc320 said:

So I did bench bleed it and that rear valve has been gone out the jeep since I have owned i andt that’s 6 years ago and rear axel has the disk brake conversion all this started right before Covid my xj was down and we were going on a wheeling trip so I took my MJ went on some trails and ripped the brake line out the axel I fixed it few months later took it out again the jeep did it again fixed that and now this problem the system did have allot of rust in the rear and when the brakes would be used the rear passenger side would lock up but now it doesn’t do that anymore