xj rear disc conversion poor rear brakes,,

i got a 00 xj with a 8.25 rear diff and 31" mtrs.. i have just installed a set of xj rear discs... don't have good pressure to my rear brakes...i jack the rear up on stands pop it in gear spinn up the wheels and stomp on the brakes and the rear doesnt lock up or come on very hard... i have removed the rubber ring off the proprtioning valve..i have also installed a willwood adjustable proprotion valve inline with the rear brake..... do i really need a proption valve?? i have bled 3 bottles of brake fluid threw the system... bleed each wheel... and don't have a good peddel feel .. peddle goes almost to the floor
1. should i remove my adjustable valve ?
2. remove adjustable valve and install a grand cherokee one?
3.install bigger m/c??

ya i have searched this but didn't find the answer

Did you convert this from a ZJ system?

I wouldn't have mentioned this but since you stated you have a crappy pedal I figured I'd throw it out there just in case....

Are you sure the calipers are on the correct side? Meaning... is the bleeder screw at the top of the caliper or the bottom?

If they are not at the top you'll never get them to bleed.

don't ask me how I know this.

Ditto the above.....BTDT.

yep... its zj brake parts.. yep the bleeders are on the top of the caliper

The next step sounds like a master cylinder. My buddy who did this with standard brakes (mine are old Bendix ABS) used a MC from a Ford E350 and got a good pedal. Try a search for that or PM Avanteone here.

mikereid350 said:

don't have good pressure to my rear brakes...i jack the rear up on stands pop it in gear spinn up the wheels and stomp on the brakes and the rear doesnt lock up or come on very hard

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mikereid350 said:

i have also installed a willwood adjustable proprotion valve inline with the rear brake

Click to expand...

So, if you can't lock up the rear brakes when they're not even on the ground why'd you install the adjustable proportioning valve on the back? I say, move it to the front and choke it down a little bit at a time and see if that helps.
Billy

confused.... where should i put the adjutable porportioning vavle?? front or rear... i have gutted my stock porportioning valve... i think next i gonna remove my the porpporting valve that i put in...

The proportioning valve, if used at all, always goes in the rear brake system, NOT the front. The idea is to stop the rear brakes from locking up, causing the Jeep to swap ends. No pressure to the rear indicates a problem in the rear system, which includes the MC, proportioning valve, rear brake lines, and rear caliper. Put a clamp on the rear rubber brake line--if doing so causes a hard pedal, then the MC and proportioning valve are probably good. If the pedal is still not hard, the problem probably is the proportioning valve or MC. I don't mean these components are necessarily bad, could just still have air trapped in them.

xjbubba said:

The proportioning valve, if used at all, always goes in the rear brake system, NOT the front. The idea is to stop the rear brakes from locking up, causing the Jeep to swap ends. No pressure to the rear indicates a problem in the rear system, which includes the MC, proportioning valve, rear brake lines, and rear caliper. Put a clamp on the rear rubber brake line--if doing so causes a hard pedal, then the MC and proportioning valve are probably good. If the pedal is still not hard, the problem probably is the proportioning valve or MC. I don't mean these components are necessarily bad, could just still have air trapped in them.

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Good info :roll:
Billy

Master cylinder. I fought my 98 with rear disks right after I installed the explorer disks untill I changed it. When you pump an old master cylinder past the place it normally rides it pushes the plunger right over the spot that all the crud has built up. This buggers up the plunger o-ring seal in the master cylinder.

JeepFreak21 said:

Good info :roll:
Billy

Click to expand...

Well, how about this.
Get a prop valve from a ZJ with discs and replace your original and dump the willwood.
Your Jeep brakes will now work as they were designed to.
I did and have no problems.

The wilwood is way better than the ZJ prop valve. It's adjustable. You can tune out lockup completely. You can't do that with the ZJ valve and it will lockup no matter what you try. Stick with the wilwood and learn to use it.