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Part numbers for 2000 XJ proportioning valve other than Mopar?


NAXJA Member
NAXJA Member
trying to help a buddy figure out crappy brakes. Stock gears, 33s 2000 XJ, no ABS, stock master and booster. we replaced calipers, pads, rotors, hubs, front brake lines, and Master Cylinder. Replaced rear springs, adjuster kit, shoes, drums and wheel cylinders. Bled the hell out of it. No air anywhere. We welded up the divits in the caliper slides too. Brakes still seem pretty bad.

We figured as a last ditch effort to replace the proportiong valve.

All I can find is the mopar 52128420AA which are 186$, so was looking for a cheaper option. There are tons of cheap prop valves for the 86-96 which is interesting. Curious if anyone knows of anything other than the 186$ mopar ones.

we have adjusted the rear brakes many times too. first thought was they might be out of adjustment but doesn't seem to make a difference.

pedal feels good just doesn't like to stop.

The only other thought I have is to double check the caliper slides to make sure we ground them flat 100%. I know we ground them pretty good and flat, but maybe there is a little hump there. The divits were pretty bad.
They really can't go bad (except for the portioning), there's got to be something you missed. Did you bench bleed the mc when perfectly level? Did you cap the prop valve tubes when you removed the mc? How are the flex lines?
Cheap disk brake pads and shoes, or good ones ? Break them in correctly, or are they glazed ?
we used centric premium cross drilled and slotted rotors, wagner severe duty pads and new unit bearings at the same time.

MC was from Napa, calipers, drums, shoes, spring kit, adjuster kit. We bench bled the MC until it was super firm. We must have bled the whole system 30 times, I cracked the lines at the prop valve and the MC many many times after bench bleeding and fully bleeding the whole system to keep checking for air at the MC and the prop valve.

We weren't getting air after the first few bleeding sessions, but after the pedal sucked so bad, we just kept bleeding in case we missed air somewhere.

I keep going back to welding up the divits in the calipers slides/knuckles thinking maybe we did not grind them flat and smooth enough. I mean we ground them flat and smooth but maybe there is a little hump somewhere.

we also swapped in longer front YJ soft lines for a 4" lifted YJ. that shouldn't affect anything.

I wonder if the wagner pads glazed on break in ?
The other thing is , even after all that brake work - he said the brakes were same as before. Which is nuts since the brakes before were terrible and the rears where totally shot with bad wheel cylinders , shoes down to bare metal, rear drums where worn all the way in .

Ive done so many brake jobs over the years, never seen this before with a firm pedal and all new components just not want to stop. We have adjusted the rears a few times now as well. cant imagine the rears getting any more adjustment
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Bad booster, maybe? Vacuum leak to the booster? Do the brakes feel the same when trying to stop with the engine off?

With everything else you've done, I'd check that.
booster was working fine we had tested it a few times with the normal booster test of turning the rig on with foot on the pedal and if it drops or not as its started and it passes. Ive had boosters fail and the pedal doesn't move once started.
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booster was working fine we had tested it a few times with the normal booster test of turning the rig on with foot on the pedal and if it drops or not as its started and it passes. Ive had boosters fail and the pedal doesn't move once started.

Then it's obvious, your legs are just weak! :laugh3: Gotta hit the gym more!

That's puzzling. Seems like you've checked everything. Keep us posted.
I would try pressure bleeding it before I went any further!
well the booster passed the start up test, it does depress at startup. But my buddy said it does make a wheezing noise when you hit the brakes so I am wondering if the booster can pass the start up test but maybe after some driving maybe it starts leaking internally and is not working?
yeah so we sourced a spare prop valve at PNP but decided not to bother swapping it in. We played with the rear shoe adjustment some more and just for fun, and we also swapped the booster . It stops better for sure, and about as good as some other friends XJs I drove this weekend on similar setup as far as vehicle weight, tire size, etc. I guess Im so used to my 1 ton brakes on my XJ, it was just weird driving a XJ on stock brakes on 33s with alot of weight, those 9" rear 8.25 drums do sort of suck.