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YellowSub2000
01-25-2010, 01:25 PM
Ok, new pads, bleeded the lines, still have a spongy brake pedal. I did convert the rear end to Disc Breaks.

Anything else to check. No air is coming out of the lines.

Mudderoy
01-25-2010, 01:41 PM
How old is the fluid? Are the lines stainless steel?

xj4life2
01-25-2010, 02:47 PM
Did you replace / add a proporsioning valve or did you change to rear disc master cylander ? If not there is your problem the master is pushing 70% to the front and only 30% to the rear like you still had drum brakes. you need to convert to the right Master Cyl.

Mudderoy
01-25-2010, 03:35 PM
Did you replace / add a proporsioning valve or did you change to rear disc master cylander ? If not there is your problem the master is pushing 70% to the front and only 30% to the rear like you still had drum brakes. you need to convert to the right Master Cyl.

Really? I read, I think here, that someone went to the D35 Grand disc brakes and didn't change master or proportion valve. No issues. Doesn't make it right, just collecting information for myself.

Voldemort
01-25-2010, 03:43 PM
Did you replace / add a proporsioning valve or did you change to rear disc master cylander ? If not there is your problem the master is pushing 70% to the front and only 30% to the rear like you still had drum brakes. you need to convert to the right Master Cyl.
Yea they will be spongy if you use the rear disc brakes with the single diaphragm brake booster that are in the early XJ's, cause the were not meant for the power of the disc brakes/

YellowSub2000
01-25-2010, 03:53 PM
I replaced the rear brakes with the Caliper system for disc brakes. Haven't changed anything else. The actually lines are stock, but the hoses to both front and rear are braided stainless.

I'll look into changing the brake booster. I read somewhere you can use on from a Grand Chero..

Any other pointers?

YellowSub2000
01-25-2010, 03:55 PM
http://www.lunghd.com/Tech_Articles/Suspension_Steering_Axles_and_Brakes/Proportioning_Valve_Mod.htm

BlueXJ
01-25-2010, 05:48 PM
So basicly he just removed the flattened o-ring from the proportioning valve and re-assembled it. This allows more fluid pressure to the rear brakes. Right???

YellowSub2000
01-25-2010, 07:37 PM
That's what I suspect. I am going get one from the Junk yard (From a Grand) and see what I can do with it.

Voldemort
01-25-2010, 11:44 PM
I have a booster, pro valve, and MC from a '97 Grand that I plan on using when I put on the rear discs from the same Jeep. Here are some good write ups http://www.madxj.com/MADXJ/technical/technicalfiles/ARbrakeBoosterUpgrade/BrakeBoosterUpgrade.htm
http://www.dippy.org/svcman/sm05d.html

YellowSub2000
01-26-2010, 06:14 PM
Went to the local junk yard to day and pulled apart a few proportional valves, for spare parts. But got one solid one to mess with. I've noticed that some of the flare nuts for the brake lines are bigger too. I'll have to look at that on mine.