Need Help Please with Brake Bleeding

I tried the search, but other threads have different isues. I am having trouble bleeding my brakes after a rear disc brake conversion. The only openings in the system were both rear lines at calipers and at the proportioning valve where I removed the cherokee stem, spring and bleeding bolt then replaced with parts from ZJ.When the engine is off and I pump the brake it gets hard. When the engine is on the pedal goes to the floor everytime. What should I do? I am using the vaccum brake bleeder tool.

09moabxj said:

The only openings in the system were both rear lines at calipers and at the proportioning valve where I removed the cherokee stem, spring and bleeding bolt then replaced with parts from
ZJ.

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you still gotta bleed all 4, IIRC.
what kinda discs did you use? are all bleeder screws mounted at the TOP?

I've yet to have good luck using one of the vacuum bleeders on either of my xj's. Best way is get a buddy and do it the old fashioned way of pumping them up then opening the bleeder valve. Just remember to do all 4 corners RR, LR, RF, LF.

xcm said:

you still gotta bleed all 4, IIRC.
what kinda discs did you use? are all bleeder screws mounted at the TOP?

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I am using Grand cherokee discs. Should the bleeder be at the top?

What would make the pedal go to the floor with the engine on, but not with the engine off?

09moabxj said:

I am using Grand cherokee discs. Should the bleeder be at the top?

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yes

09moabxj said:

What would make the pedal go to the floor with the engine on, but not with the engine off?

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brake booster leak

Even with massive brake booster leak, pedal should not go to the floor. The brakes are meant to still work (with high effort) even if the engine stalls. If you have no external leaks, the master cylinder is probably bad. You are just too weak to make it go down without power assist. Push harder!

Thanks for the help. I had the calipers on the wrong sides and didnt bleed the proportioning valve good enough. Rear disc conversion is an awesome upgrade.

Yep, the bleeder valves have to be on the top of the caliper.

I'm usually doing stuff myself, so I've always gravity bled my brakes and it's always worked just fine. Crack the bleeder valve and let it drip slowly for awhile (into a container) and check the fluid level now and then. Perfect for when you're working on some other part of the vehicle.

New Question: I removed the xj stem, spring and cap out of the proportioning valve and replaced them with ZJ parts. The ZJ parts are different diameter stem, different spring rate and cap to match up with the stem. After reading rear disc brake conversion threads this seems to be the best thing to do to make sure the front brakes function before the back brakes. I am thinking that now it takes to long for the rear brakes to function after the fronts are already breaking. Has anyone done something different with the proportioning valve? Maybe XJ spring with ZJ stem and cap? I have noticed a improvement with the conversion, but I want to get more out of it. Seems like a lot of people are not happy with there conversion which they might not have the right proportioning valve set up.