YJ master cylinder upgrade

Jeremed

Jeremed

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[TD="class: alt1, bgcolor: #000000"]I have looked at some of the other threads and couldn't really find the answer, so here it is. I have a 94' YJ. I just put a 14 bolt in the rear with a disk brake conversion and a Chevy Dana 60 up front. I started out with a 99' dodge 3/4 MC and a stock YJ booster. I do not have a proportioning valve. If I adjust the push rod out to where the pedal feels good and the brakes work amazing. About a mile down the road I can feel the brakes starting to grab and heat up. I then have to loosen the nuts holding the MC on the booster a few times to relieve the pressure. If I adjust the pushrod so it isn't putting pressure on the MC when I bolt it up, my pedal goes right to the floor and my brakes are useless. I also just tried a MC from a 78' grand marquis and I am running into the same issues. Any help is greatly appreciated.
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Hmmm. Im not going to be much help but im running a ford dana 60 front, and a dana 60 rear with a disk conversion in my YJ. Im using the stock YJ master cylinder and stock proportioning valve. My brakes work fine and thats with my rig being 5000# and on 37s. I have a ford van master cylinder i thought about swapping in, but havent yet. Perhaps you could try the stock cylinder?

I know the pushrod is not supposed to be touching the piston when you install it. Other than that it almost sounds like not enough fluid is being sent to the calipers when you have the pushrod set correctly.

Hopefully someone with more knowledge will chime in soon.
 
Exactly...I have even lengthened the linkage that connects to the pedal hoping it might increase my throw. It only moved my pedal up 2" and now it stops 2" from the floor. And my brakes still suck!
 
Cardone part number 10-1534. You might need to change the length of the pushrod a bit to fit it.
 
I did a rear swap on a nine inch in the back of my 88 yj. The stock master worked but I wanted more pressure so I used a mc from a 69 vette with rear disks. I had to open the holes stlightly and lengthen the push rod but I did increase the pressure. I also found some info on modifying the prop valve?
 
i run a stock setup with discs front n rear and an adjustable valve and i still can lock up all 4 39.5x16.5 rockers on the street
 
Did the donor MC vehicle have rear disk brakes? If I remember right the 90's dodges still had drums. I would try a MC out of a vehicle that had rear discs. Disc brakes require more fluid to operate than drums, the bore size on your MC is probably to small to push enough fluid to the larger capacity disc calipers without already being preloaded.

Not sure, as i'm no genius just my thoughts
 
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