Swapping A Proportional Valve

[Hudson]

When i swapped rear discs into my XJ, i grabbed the prop valve from the junkyard but never swapped it in. My brakes are starting to go the floor again and i think it's a combination of bad brake pads and an inadequate prop valve.

I'm going to put in new brake pads tonight and re-bleed the system so i figured i should swap it in now.

I have the ZJ prop valve sitting in my garage, but i think i need to do something to it to make it work. How would i swap a ZJ prop valve into an XJ?

Dummied down instructions would be a plus.

[justtorchit]

You could try reading your last thread about your brake issues.

look for fluid leak if not probably a master.

The prop valve is not the problem. You should do some research to figure out how they work and you will figure it out if anything it will make your brake pedal harder.

drum brake prop valves have a residual pressure check valve if you leave it in it will make the rear disk brakes drag. the extra pressure is needed to counteract the springs in the drum brakes.
You can simply remove the O-ring on the check valve just unscrew the large bolt in the front of the prop valve remove the o-ring and reassemble. easier than changing the whole valve. you will still need to bleed.

[justtorchit]

My brakes are starting to go the floor again and i think it's a combination of bad brake pads and an inadequate prop valve.

My first post might have been a little assholeish so ill try and help

First your reasoning for why your pedal is going to the floor dosent make sense.
worn brake pads wont make your pedal go to the floor. Your "inadequate" 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.

When you hit the pedal it pushes a piston in the "master" and pushes the fluid to the calipers pistons... The only way you are having the pedal go to the floor is if the master cylinder is bad (fluid is not getting pushed into the lines, bypassing, therefore no pressure pushing on the calipers) or you have a leak (fluid escaping system), or you have air in the lines creating a mushy pedal.


And yes you can change the proportioning valve but its not your propblem

[Hudson]

My first post might have been a little assholeish so ill try and help

First your reasoning for why your pedal is going to the floor dosent make sense.
worn brake pads wont make your pedal go to the floor. Your "inadequate" 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.

When you hit the pedal it pushes a piston in the "master" and pushes the fluid to the calipers pistons... The only way you are having the pedal go to the floor is if the master cylinder is bad (fluid is not getting pushed into the lines, bypassing, therefore no pressure pushing on the calipers) or you have a leak (fluid escaping system), or you have air in the lines creating a mushy pedal.


And yes you can change the proportioning valve but its not your propblem

No offense taken. I should have went back and re-read my previous thread to see if it had been stated before creating a new thread.

Thank you for the information. Makes perfect sense and actually clears up all of my questions.

I'm going to begin looking into a master cylinder upgrade and see what needs to be done to do that. If it's broken i might as well upgrade it.

Will the ZJ prop and the XJ prop work identical when the o-ring is out of the XJ one?

[justtorchit]

No offense taken. I should have went back and re-read my previous thread to see if it had been stated before creating a new thread.

Thank you for the information. Makes perfect sense and actually clears up all of my questions.

I'm going to begin looking into a master cylinder upgrade and see what needs to be done to do that. If it's broken i might as well upgrade it.

Will the ZJ prop and the XJ prop work identical when the o-ring is out of the XJ one?

i was going to say i think certain zj prop valves (obviously rear disk) will work.

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.



thats the basics of the valve... im not saying dont swap it..... more of just saying thats not your problem.

i wouldnt bother "upgrading" your master either... sounds good and dandy but the size of the piston in the master is perfect for your set up. if you were running big dual piston calipers on all 4 corners then you would have the need. but you dont.



so my walk through for you:

put your new pads on,

pull the oring from the stock valve

check the fluid level,

bleed your brakes, starting from passanger rear, to drivers rear, to passangers front, to drivers front. take your time and be sure to get rid of any air.

after you are positive there is no air or leaks in the system, take it for a spin and see how the pedal feels and how the jeep reacts with 50/50 proportioning

if the pedal still goes to the floor, put a new STOCK master in. be sure to bleed the master before you install.

now if its stillllllll going to the floor..... roll your jeep off a cliff



once you figure out your pedal to the floor problem then maybe switch to teh zj prop valve if your feel its neccesary

[konastinky1234]

the zj valve worked out great for me when i did it with the 8.8 discs. never bothered with the pulling the o-ring method just went straight to it and the brake setup has been great in terms of the proportioning.

torchit is definitely right there, the problem sounds like it is definitely some type of air in the lines somewhere. when i did my 8.8 i put the calipers on upside down so they could not get the air bled out of them no matter how hard i tried and the pedal was to the floor. once i flipped em they were golden. only reason i say that is i overlooked it like an idiot and took a week to figure it out.

also recently my yukon had a rotted brakeline that slowly put the pedal further and further to the floor over like a 6 month period. seems like it could apply to your situation in that there would be a very tiny, slow leak in the system somewhere if that is the case.

just some info in case you overlooked anything like i did 3 years ago.

[CumminsJeep]

I gotta say, I never touched my prop valve when I did my 8.8 swap and they are great. No dragging at all either. The thing stops better on 35s than my semi-stock xj on 31s with brand new brakes all around.

[ninetysix-ex-jay]

I gotta say, I never touched my prop valve when I did my 8.8 swap and they are great. No dragging at all either. The thing stops better on 35s than my semi-stock xj on 31s with brand new brakes all around.

Same here

[justtorchit]

I gotta say, I never touched my prop valve when I did my 8.8 swap and they are great. No dragging at all either. The thing stops better on 35s than my semi-stock xj on 31s with brand new brakes all around.

like i said. so little difference you wouldnt notice and i dont see the point of swapping valves....

[Burton58]

Me too, never did the valve on 35's and disks. In fact i still have one laying around cause i didn't use it

[HeavyMetal]

Me too, never did the valve on 35's and disks. In fact i still have one laying around cause i didn't use it

mine?

can i has? srs

black jeep is a bastard with brakes

[hippie metal]

That thing still has a braking issue?

[Burton58]

mine?

can i has? srs

black jeep is a bastard with brakes

Yeah lemme find it and you can have it. Includes a free d35 too

[CumminsJeep]

Yeah lemme find it and you can have it. Includes a free d35 too

[HeavyMetal]

Yeah lemme find it and you can have it. Includes a free d35 too

could be the worst deal ever