Grand Cherokee Master Cylinder and Brake Booster Swap

yah i had a 6pt 13/16 on
it and just a cresent wrench on the valve body
ill do channel locks tonight
or ill just pull the lines and pull the prop valve out
put it in the vice
they have always come right off at the jy
maybe ill have my roommate hold the channel locks or something while i carefully turn
 
yah i had a 6pt 13/16 on
it and just a cresent wrench on the valve body
ill do channel locks tonight
or ill just pull the lines and pull the prop valve out
put it in the vice
they have always come right off at the jy
maybe ill have my roommate hold the channel locks or something while i carefully turn
 
Few questions about this since I think I'm finally gonna tackle it this month.

94XJ, I have a 96 Master/Booster. Running an 8.8" with discs on the rear.

Are the 96's lines on the drivers side like the WJ booster?

Does it use the same style flare as the WJ booster or as the XJ booster?

I've had this booster for a while, been sitting in my parents garage. Anything I should be worried of condition-wise for this thing (haven't looked at it since I bought it 2 years ago)? Is rust on the previously cut lines something I should worry about (basically could it have caused the rust to spread to inside the booster?

Since I'm running rear discs, should I modify (or replace with a ZJ) proportioning valve?

Thanks
 
the rear disc zj valve has a shorter spring with a higher spring rate
i just swapped springs
and left the little rubber oring in there

and on my renix the prop valve bleeder and access to the spring was a 19mm not a 13/16
.
also bled it all again(flushed it real good too) seems to stop so much better, but i wont be able to tell until ive realy driven it more.

wj booster is bubble flare
xj prop valve ends are double flare
i used the wj lines and put the xj prop valve fittings at the prop valve ends.
then bent them accordingly.
seems to work fine so far.
 
I just pulled the 96 booster I have out of storage and found its missing the spacer.

Thinking I'll hit the yard this week to see if I can snag one (and practice dis assembly).

If not, can I just space it out 1/4" with some washers or other material I have at home?
 
Finished this mod a few months ago but finally pulled the jeep outta the garage for the first time since October. My DD is a 96 V8 ZJ for air conditioning. I generally only drive the XJ when its cool enough outside for no AC or when i want to pretend i am cool. First impression was actually none. I forgot i had swapped boosters, the XJ stopped exactly like my ZJ. What a great easy mod for us with older XJ's. The jeep finally stopped like a normal stock vehicle should. I definitely recommend that anyone who hasn't done the swap yet or who is thinking about doing the swap to get on it immediately. It is one of the best mods i have done so far and i finally feel safe driving my turd in traffic. The difference is absolutely night and day to what i remember back in October.

My swap went extremely easy. I picked up a 98 XJ booster and MC from the local pick and pull. I made sure to grab the nuts from the inside of the vehicle and the brake lines which routed from the drivers side of the MC to the passenger side of the MC (so i wouldn't have to do any soooper tight brake line bending). I removed my almost brand new 87 booster and MC and mocked up the 98 stuff. I left the Styrofoam spacer in between the booster and the firewall. New stuff was hitting the washer bottle so i unbolted it, then removed my air box for some more room. Put the booster back in the hole again and the fit was perfect. I did not have to massage my firewall or add any spacers. The push rod was too long on the inside and the brake switch was not going to work with the round end of the push rod. I decided i was just going to cut the old push rod end off the 87 booster and weld it on the 98 booster push rod. I then measured how much lower i wanted the pedal to sit and removed about two inches from the 98 push rod (don't quote me on the measurements, this was a few months ago). I beveled the edges on the 98 push rod and did the same to the 87 push rod end. Pulled out the trusty millermatic 35 and tacked everything together for a final placement check. Mocked it all up and everything fit together fine, even the brake light switch was working properly. Did the final welds on the booster push rod and ground everything down smooth and reinstalled. For the brake lines i picked up some couplers from Checkers (O'Reileys) and pre-flared brake lines. The brake lines had flares already installed on both ends and new flare nuts all i had to do was bend em to fit. I discarded my old brake lines which ran from the prop valve to the old MC. Used my Harbor Freight brake line bender (blue one that looks like a nutcracker) which made the job real easy. No kinked lines and everything fit together real easy. I then bench bled the MC and then all four wheels using a mighty-vac bleeding tool. Checked the pedal and i was good to go. Next i decided to just move the washer fluid bottle forward an inch or so to clear the larger booster and then reinstalled the airbox ect. It was a really tight fit but i got it all in there.

All and all took me an entire day to finish this mod. Most of my time was spent hunting down brake adapters and couplers. I had originally tried to flare my own lines using the old flare nuts but i broke my flare tool and decided to rent one from Checkers rather than buy a new one. When i asked for new brake line they handed me one with two flared ends with nuts already installed. I hate flaring brake lines so i just bought two lines of the right size and approximate length. These new lines made this swap a ton easier and took away a lot of frustration. Checkers has a small selection of brake adapters and couplings which can be used but a better option i found out later doing another project is to goto Ace Hardware. They have a much larger selection and are a lil cheaper.

Do this mod. Its easy and brakes work so much better after.

Good Luck
-Mike

87' XJ, 4.0, AW4
44 stock drum rear, 30 stock disc front
stock prop valve
35" swampers
 
John - yeah, I used stacks of 1/4 or 5/16 washers, forget which. Use as many as you need to, measure from the booster mounting face to the center of the pushrod hole on each booster and space the new one enough to match.
 
the 97+ XJ gear is dual diaphragm, yes, but a different unit than the WJ booster - and harder to swap in to an older rig than the WJ unit. make sense?
Not really, but thats how it goes
 
kastein said:
Bump for great tech!

Well... I finally bit the bullet and did this mod. Some of my (maybe useful) input is below.
Click to expand...

I'm getting ready to buy a 99-04 WJ master/booster to do the swap on my 89 MJ. What did you do about the rear load-sensing valve? I already have rear discs from a Crown Vic installed, so I was thinking of just eliminating the load valve and extra plumbing by using a prop valve from a rear-disc equipped ZJ. I figure if it's really unbalanced, I can get a Wilwood adjustable valve and put in the back.
 
I left the valve in place, since I daily drive the MJ with anything from 0 pounds to a dozen 3/4" sheets of plywood or an entire XJ drivetrain in the back. If you don't mind adjusting by hand with a Wilwood valve, go for it, it will be more reliable most likely.

Funny you bring this thread back up, the WJ booster I got just crapped the bed this morning. I get a rather loud rushing sound when the throttle is closed or I'm releasing the brake pedal, it's got a bad vacuum leak in it somewhere from the sound of it. I am not sure if it's due to the angle the pushrod ended up at, or because I "saved money" by not getting the warranty from the pull-a-part when I bought the booster :doh: though it would have ended months ago anyways.
 
The 95-96 dual diaphragm booster is a bolt in to the earlier rigs, just get the pedal with it. It even comes with an aluminum spacer plate to make the angle right, no stacking washers. Way less work than the WJ. Also all the XJ, ZJ, WJ had 1" bore master cylinders.
 
Hey Guys, so I've got a question.

Ive got a 91 XJ and the ABS went out on it. The pump is "shot" and the MC is losing pressure. Im looking at swapping out for a basic MC and Vacuum booster but im not sure which jeep would be the easiest to swap. I would really like to have a dual diaphragm booster if its not that much more work. Let me know what you guys think.
 
I have an 86 XJ wagoneer with a 4.0L Renix system installed, and I have an WJ brake booster and master cylinder that I want to install, any things I can expect to be different from the newer XJ's with the OBD systems, I wanna make sure i have all the stuff before I get started.
 
What is the difference between the WJ and ZJ Brake boosters/ Master Cylinders? I ordered a WJ from someone and I think they send me a ZJ. It's not worth the money to send it back, can any one tell me if I will have any problems doing the BB swap using the ZJ BB and Master Cylinder? Anyone run into any snags? Are spacers needed?
 
I'm started this swap this week. I have a 91 xj. I got a. 2000 wj mc/booster from jun yard. I'm using the same porpportioning valve from xj since the junk couldn't give me one. I have mounted the booster up with and without spacers and th push rod still doesn't line up right, does this sound familar? I ended up pulling the pedal out to drill new hole butCan I use a bolt to attach the push rod and pedal or should I just use the OEM pin since they need to have a Smith surface to pivot ? I'm also having trouble flaring the lines you guys have some tips or secretes? Thanks
 
Sry to be douchey & not research better, but I browsed over this post earlier... I'm @ the JY right now, found 2 GC's with the dual diaphragm boosters (tho they are painted red for cash with clunkers). I have an 87 Cherokee. No ABS. will it matter what I pull from the JY? I'm assuming any newer model will have ABS... Hopefully I can get an answer before I leave...
 
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