Brake problems

[HeavyMetal]

Fun facts:

No air in system we can see.
No leaks, no loss of fluid over time.
Bled over and over.
Solid pressure when Jeep is off.
When you turn it on, the pedal is very very spongy and goes almost to the floor but will lock the fronts up when hammered...will not lock the rears up or use them much. Brake dummy light is not illuminated, but I know it works as it comes on when bleeding and reaching the low point in the pedal (obviously)

Been this way for 2 completely different rear axles.
Stock drum rear, stock discs front.
ABS equipped Jeep that the wires have been cut. (no more ABS rear axle.)
brand new rubber lines.
cant even lock the rears on gravel.

2000 XJ

any opinions?

[clean4drxj]

I had ABS and deleted it and have had the same issue, I believe it to be part of the rear brakes being out of adjustment and the fact that the ABS is still there maybe haing something to do with it.

[ct67_72]

Try this. Remove the valve from the proportioning valve. Remove this rubber grommet piece. reinstall the valve, spring and retaining bolt.


If you dont notice any difference I would remove the rear brake hose and check it for a restriction, possibly the rest of the line too. If the hose is off, pull the line from the prop valve and blow air through it.
I have seen the rubber hoses come apart and block up the line.

[HeavyMetal]

interesting...i did that on my green jeep when i did the rear discs..would be worth a try on this one I suppose. easy enough

[crosbike]

interesting...i did that on my green jeep when i did the rear discs..would be worth a try on this one I suppose. easy enough

I dont think ive ever seen you refer to heavy as my green jeep. Mind. Blown

[HeavyMetal]

I dont think ive ever seen you refer to heavy as my green jeep. Mind. Blown

i did it in hopes of you watching

[ct67_72]

I figure it cant hurt, it will put some more pressure to the rear, maybe it will make a difference.

[Burton58]

i thought that puts less pressure to the rear?

[HeavyMetal]

as far as i understand it, when you do a disc swap on the rear it requires more fluid pressure than with the drums, which is why you do this mod normally ..so for this circumstance maybe itll make sense.

[Burton58]

ah thought the disks took less pressure. hope this works, if not i have the zj one for ya

[Hudson]

I've been told so many different things about what to do with the prop valve when you do a disc brake conversion that i've lost count.

Your prop valve is doing nothing more than leaving pressure in the lines creating your rear brakes to drag...... simple 2 minute fix is what justin stated.

the xj prop valve with the o ring removed will be 50/50 (100% of the pressure forn the master to the rears and fronts), but your rear pads wont drag all the time. i have run this set up and i personally didnt mind it. less work, didnt have to buy a valve and it was fun in the snow and rain (if i slammed the pedal the rears would lock up first becasue there is less wieght) its not like its un controlable and i could barely notice driving normaly.

the disk brake zj valve wont have the residule pressure check valve for the rears, and it is more than likely like 70%. sending 70% of the pressure applied by the master to the rear and 100% of the pressure from the master to your fronts.

If i were you i'd check the hard lines to make sure those aren't clogged up or bent or something along those lines. Or as someone else stated you could blow some compressed air through them to attempt to "clean them up".

[HeavyMetal]

I guess I dont see how the lines could be clogged up if when bleeding the fluid just flows freely and cleanly through everything

[ct67_72]

I guess I dont see how the lines could be clogged up if when bleeding the fluid just flows freely and cleanly through everything

Might not be clogged, but more restricted. Enough to pass fluid bleeding, but not enough volume to brake.
Still drums on the back? Do you know that they are adjusted properly? Is the E-brake connected, and if so how far up will it pull?

[HeavyMetal]

it has drums but all 3 axles that have been under this has been drums so i find it hard to believe it would be drum adjustment problems across all of them (i could be wrong)

no ebrake (cord cut off)

[ct67_72]

Did you actually adjust the drums when the axle went in? Very common for the adjusters not to work and would do just what you say it does. I dont think I have ever driven a Jeep with the drums adjusted correctly minus my own.