Grand Cherokee Master Cylinder and Brake Booster Swap

[1990JEEPXJ]

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.

less work but then the washer bottle wont fit, correct? i need to get a new MC/booster ASAP and am on the fence about 95-96XJ combo or a WJ set up.

and also, with the WJ booster, someone addressed that the pushrod is at a somewhat severe angle at the brake pedal. any issues with this? is the only fix going to be cutting off and welding on the end of the pushrod from my 90?

 

[1990JEEPXJ]

two more questions, when doing this swap, i cant seem to get the booster to sit flush against the firewall. would using the spacer from a 95-96 XJ help? i already massaged the pinch seams so the booster itself fits in there.

also, the hole in the pedal and the booster rod dont line up well. is there any issue with drilling a new hole? i know this will change the throw of the pedal and the leverage, but anything else? bad idea?

and this is on my XJ that had ABS.

 

[1990JEEPXJ]

ok so i just finished this swap and it went fairly smooth minus one thing, the pedal was super soft and the brakes would engage very late in the pedal throw. now, i noticed that starboards original booster in his 89 had a bend at the end of the rod, the rod on my ABS M/C, was not bent and was straight just like the WJ booster rod. so i decided that on non-ABS XJ's the hole in the pedal that the booster rod mounts to is lower. so i went ahead and drilled a new hole a little lower and slightly closer to the inside of the firewall, MUCH better pedal feel. barely moved the pedal closer to me but made the pedal throw much shorter. it feels way better that way. it also does not put any strain on the rod as i put it so the WJ rod is sitting straight and does not bend up or down to mount to the pedal

other than that it was a pretty simple swap.

 

[1990JEEPXJ]

one last question, what is the layout of the prop valve? from thie write up is looks like front of the MC goes to front of the PV. but what about the outputs? there are three, two on the bottom and one on the back. each front will have its own and both back go into one. so which outputs go to which?

 

[Cottontail]

Alright, I read the thread front to back and back to front and there are 2 items that either weren't covered, or weren't covered to the degree that I felt comfortable answering my own questions.

1. I have a 2001 XJ. Seems that some guys did this swap on a 2000 XJ and felt that it was a good upgrade, and others that said that doing it on an XJ this "new" wouldn't have any affect and that the 2000+ XJs already have good braking booster/MC

2. I have disk brakes and an Explorer 8.8 on the rear. Is there anything special/additional that I would need to do on a swap like this due to the Ford rear end?

Sounds like a valuable swap, and would be another good learning project.

Thanks y'all!

 

[1990JEEPXJ]

one last question, what is the layout of the prop valve? from thie write up is looks like front of the MC goes to front of the PV. but what about the outputs? there are three, two on the bottom and one on the back. each front will have its own and both back go into one. so which outputs go to which?

bump, anyone?

 

[1990JEEPXJ]

TTT. no one can answer this? i figure it will be a big help for those of us who removed the old style ABS and had a funky prop valve lay out where only three of the five ports were used.

 

[Uhrinator]

TTT. no one can answer this? i figure it will be a big help for those of us who removed the old style ABS and had a funky prop valve lay out where only three of the five ports were used.

I think I have found what you need. I did this a while ago too and I took off my prop. valve. So from the front of the prop. valve closest to the grille, the under line goes to the rear brakes and the rear under line goes to the left front brake and the rear upper line goes to the right front brake. I'm pretty sure this is right. I found the diagram here : http://www.jeep4x4center.com/knowledge-base/index.htm#service on page 21. It says that its for a yj, but it looks almost the exact same as the other xj ones. Hope this helps.

 

[aintright]

so one thing that i didn't see mentioned was the proper fittings to use on the 99-04 wj master cylinder.

the fitting closest to the firewall is an m10x1.0 metric fitting for a bubble flare

the fitting furthest from the firewall is an m11x1.0 metric fitting for a bubble flare

probably going to have to go to the dealer to find the m11x1.0 metric fitting. they were closed today and i struck out at 3 different parts stores. they didn't even have the brake line that i could cut up to use.

be careful a standard fitting will thread into it, but it is the wrong fitting to use. it won't seat properly on the bubble flare. this could be why there are so many posts about having a hard time bleeding the system.

the best way i found to bench bleed the master cylinder is in the jeep. get some clear plastic tubing that will slid over your 3/16 brake line and run the tubing back into the master cylinder.

flare to small, straight pieces of line and use the proper fittings and tighten down in the mc

take your clear tubing and slide it over the 3/16 line, then run the other end of the plastic tube into the mc resevoir

push the brake pedal down very slowly watching the bubbles. slowly release the pedal a little bit, but hold it there and watch the bubbles rise. then push the pedal slowly back down.

repeat this until you don't see any bubbles at all in the lines.

if yo pump the brakes too quickly you'll aerate the brake fluid.

 

[kastein]

Easy way to deal with the wonky fittings on the MC is to just get the lines at the JY (with the MC, or get them separately if you buy a new MC) and reflare the other end, as they are standard 3/16 hardline. I never even unscrewed the special MC fittings.

 

[Vanimal]

i have a 94 zj for parts with this exact style booster/master cylinder. is this dual diaphram and/or worth swapping into my xj?

 

[bails85]

I have an 8.8 in my xj with discs. Being that the wj runs 4 wheel discs wouldn't this just be a straight swap? Without having to mess with the p valve? I would like to think that the xj and wj are close to the same weight. I talking in theory here and I really have no clue so someone correct me if I'm wrong. Gracias

 

[Fred]

WJ is heavier.

 

[aintright]

so i need to correct one of the fitting sizes. the correct size is m12x1.0 with a bubble flare. NOT m11x1.0

sorry for any confusion

yeah i bought the mc new and didn't have the lines. i ended up just getting an m12x1.0 adapter to m10x1.0 with an inverted flare and all was good.

now if the damn jeep would just start

 

[kastein]

If it doesn't start, a wj booster/master is way overkill for the amount of stopping you need to do... :laugh2:

 

[krawler09]

Why would my brake lights stay on all the time? Ive got an 88 I am in the process of doing this mod on.

 

[Muad'Dib]

Why would my brake lights stay on all the time? Ive got an 88 I am in the process of doing this mod on.

So you have swapped the booster and now your brake lights stay on all the time?

Sounds like you didnt take enough material off the end of the booster rod and now its putting constant pressure on the brake light switch.

 

[Vanimal]

anyone know if a master cylinder from a 94 zj 4.0 would be worth swapping in? i have a zj for parts which is why i ask. this has been asked in here i dont know how many times so far any noone has answered.

 

[bails85]

No.

 

[bails85]

Does anyone know if the wj brakes will fit under a 15 inch steel wheels with 4 inch bs?