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4wheel disk master cylinder

S

scampbell53

NAXJA Forum User
Location
Clarksville, TN
I know have for wheel disk brakes. My master cylinder just can not push enough fluid. (90 XJ by the way) Does anyone know if a zj master cylinder will bolt in? Or any other good ideas. Thanks.
 
If you have a non ABS system, an easy way to get fluid to those brakes is to REMOVE an O-Ring in the proportioning vavle. There is a screw/bolt in the block, at the end, there should be a ring. If there isn't, it is stuck inside, I had that problem. Once that is out, your rear brakes are ganna be great.

Matt
 
IIRC the ZJ master is the same part nubber as the XJ, but the prop valve is different. If I could get all the stuff out of boxes (dual booster, new master, ZJ disc/disc prop valve) and on to my XJ, I'd be able to tell you how well it works..........try the o-ring removal in the XJ prop valve first, it may satisfy your needs.
I've run the SVO rear disc kit on my 89 for a few years and the braking is adequate with the o-ring removed. Stops MUCH better than stock and there is no fade when on the brakes hard, running 32's FWIW.
 
Have a write up on my site on removing the O ring if you want to do that. The above information is right that the M/C is the same. I had tried the O ring removal trick but it caused my rears to lock up and reduced my braking. It does depend of what size the pistons in the rear calipers are to what will work for you. Which ones did you use? The sign that the master is too small for them is that it will be much nearer to the floor before braking starts. Is this what is happening?
I am about to fit a ZJ p/valve myself as soon as it gets here so I will have a full factory setup.
More info on my site.
 
Why is it that the brakes on my wifes TJ that has 33's work so much better than our XJ's with larger tires? Is it possible to use the TJ brake set up? Not really helping you, just curious if someone knows.
 
I have heard about the o ring removal. I am in the middle of doing this disc conversion on my XJ d44. I would prefer to do something a little more exacting than just removing an o ring although it may be the answer. Here is a site on a TJ that looked good. Not sure if I can do what is on this link?

http://www.stu-offroad.com/brakeconv/bc-6.htm

Curt
 
Yeah I have one ton brakes front and rear. The pedal takes A LOT of travel to get them to work. I don't have any problem stopping but I think the new calipers are just to big for the master cylinder. Any other ideas for a new one?
 
I'm running 3/4 ton Ford front rotors (dual piston) and 3/4 ton Chevy rear rotors. The solution to my braking was the E250 M/C, $21 at Autozone. You have to grind it a little to fit in the booster, but it's no biggie. I can now stop on a dime with 38s. I'm running the stock '89 single diaphram booster.

I first tried making it work with the stock M/C and there just isn't enough volume. The pedal would go straight to the floor with NO effect.

Alot of people will say there's more pedal effort with the bigger M/C piston, but I dont notice any. I swear these brakes are better than anything I've driven, I've got full lockup with NO pedal pressure at 1/2 pedal travel. There f*cking awesome.
 
scampbell53 said:
That was the answer that I was looking for! Any paticular year you used? Thanks!
Click to expand...

I think it's an '86. The Autozone part # is M2008, the Napa part number is 10-2008. I gave them back my XJ m/c as core, gotta love those guys. :)

You can look it up & even order it online from autozone.com or napa.com .
 
Would there be a negative effect of putting the E250 M/C in place of the stock unit but keeping the stock Dana 30 brake components and Ford 8.8 rear disks?
 
After actually DOING this mod, I'd say no. With the smaller pistons you will have more than enough pedal.

-jb
 
Thanks Vintage, I was just wondering it the bigger M/C would make the brakes too good, as in they lock up if you even breath on the brake petal. I want the brakes good but not so good that I cant use them with out flat spotting the tires:D

Thanks

AARON
 
I used the '86 E350. don't know if it's the same as the E250 or not.
Works good but I don't remember the price being $20 either:eek:
 
Vintage....are you running a stock 89 combo valve? With or without the o-ring?
I have yet to do my 96 dual booster, master and 4wheel disc ZJ combo valve swap, need to get it done cause I'm tired of moving the parts around in my garage........I'm running stock brakes up front with an SVO (Explorer, same as ZJ) disc kit in the rear. I do have the O-ring pulled from combo valve and the brakes are better than stock, but could be better still.

Wonder if the bigger M/C would be enough..........definitely be less work, but I'm going for the best ROI overall.
 
You want to use the smallest bore MC that will displace enough fluid for your brakes.A larger MC requires more "foot" pressure to get the job done.We just did a 8.8 conversion on my buddys Jeep.It was "ok" with the stock prop. valve,not much better w/ the o-ring removed,"way" better w/ boneyard ZJ valve!
 
RCP Phx said:
We just did a 8.8 conversion on my buddys Jeep.It was "ok" with the stock prop. valve,not much better w/ the o-ring removed,"way" better w/ boneyard ZJ valve!
Click to expand...

What year was the Jeep....i.e. single or dual diaphram booster?
 
XJEEPER said:
What year was the Jeep....i.e. single or dual diaphram booster?
Click to expand...

The Jeep is a 93 w/ single diaphram,the donor prop valve came out of a 96 4-wheel disc ZJ.Also used MORE e-brake cables that worked nice also!
 
XJEEPER said:
Vintage....are you running a stock 89 combo valve? With or without the o-ring?
I have yet to do my 96 dual booster, master and 4wheel disc ZJ combo valve swap, need to get it done cause I'm tired of moving the parts around in my garage........I'm running stock brakes up front with an SVO (Explorer, same as ZJ) disc kit in the rear. I do have the O-ring pulled from combo valve and the brakes are better than stock, but could be better still.

Wonder if the bigger M/C would be enough..........definitely be less work, but I'm going for the best ROI overall.
Click to expand...

I'm not running a proportioning valve. Which sucks cause I bought one before I finished the brakes. The balance is just right and the brakes are so good that I'm changing my order from the 4.0 Atlas to the 4.3. :)

I had actually done the o-ring removal with my old setup (discs on a D44 rear front D30) and I wasn't impressed with it at all. Made no difference, the brakes just plain sucked.

-jb
 
RCP Phx said:
You want to use the smallest bore MC that will displace enough fluid for your brakes.A larger MC requires more "foot" pressure to get the job done.We just did a 8.8 conversion on my buddys Jeep.It was "ok" with the stock prop. valve,not much better w/ the o-ring removed,"way" better w/ boneyard ZJ valve!
Click to expand...

Yea Phx, I read that thread too but I did the switch anyway. Maybe it's just my mix of parts but there is hardly any pedal "pressure" it's actually super easy to press, kind of like a Cadillac. And I've got 6 really big pistons to push......
 
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