soft brakes 87 cherokee 4 L

[mnorvold]

Perhaps there is are wise brake men out there. I have very soft brakes on my 87 cherokee laredo, discs front, drums rear. New rear brake cylinders and new MC. I have bench bled the MC and the system 3-4 times, no air. I bled FR, FL, BR, BL. I performed a simple pedal test from the Haynes manual to prove the booster. There is vacuum in the booster. I can pump them to get a more firm pedal. Sometimes, after a slow turn (left or right) as I apply the brakes there is nothing. Thoughts? Prop valve?

[JohnnyJ]

is this for a stock system, or some random mix of parts?

[mnorvold]

stock, almost mint for it's age and 255,000 miles

[Budd]

'd

Bleed from the farthest brake from the m/c first.

[mnorvold]

I have done it both ways (neither helped) but the manual and other posts have shown that the fronts must be bled first to set the proportioning valve i guess

[VancoPBS]

Adjust the rears. They should drag to the point that if you spun them as hard as you can with the tire on it only makes one revolution.

[MDMIKE]

Check into swapping the 96 or newer booster and MC from an XJ. I know I've seen quite a few write ups on here and over on NAXJA. Makes a world of difference. I know theres an issue with the throw of the brake pedal on the older XJ's versus the newer ones, but I believe theres an easy fix for that as well. Search it up!

MIke

[xgeekstarx]

get the whole booster/mc from a 95-96 XJ and it will be a direct swap. all you have to do is rig the brake switch and bend up two brake lines. in 97-up they used a lot longer rod in the booster that wont match up. put one in my 92 and it's like night and day.

http://www.madxj.com/MADXJ/technical...terUpgrade.htm
there's a write-up.

[mnorvold]

Thanks. I've done all the adjusting and replacing I can. The only thing left is this swap? The brakes worked well 'til 2 years ago. I guess the swap is all that's left?

[xjaddiction]

I swapped a '92Ford E-350 master cylinder into my MJ (I've got Waggy D-44's under it). Bolt on except for the front brake line which requires an adapter from auto parts store. I went to a pull apart for the master cylinder. Total project took about 15 min. to install, and about 30 min. of driving and making adjustments. Total cost was less than $20. The brake pedal is firm... I like firmness, will just about lock up the 38's. Stopping distance is alot shorter. Best 20 bucks I've ever spent for the MJ.

I had to adjust the push rod out a couple of turns to get them where I wanted them. Driving the beast is alot more fun now.

A friend of mine, that figured all this out, has also used a '90 model E-350 MC

[andyr354]

The swap only makes the booster stronger to help you out more. In my opinion you have air in the system or a rear out of adjustment.

Do you have to push the pedal a ways to get the brakes to work? That is a major sign of a rear out of adj. The way you also have to pump the brakes is also a giveaway to this condition. Gotta push enough fluid to get the shoes back in contact.

Also do you have the crappy old Bendix ABS?

[mnorvold]

the pedal does travel a bit before i feel resistance. I'll check the rears again but they did drag to the point of hearing a little friction. I know what you mean by pumping but even at that they are never rock hard. This all started after I replaced rear pads and cylinders about three years ago.
No, this is not ABS

[Steve N]

[Slagburn]

Originally Posted by mnorvold

Sometimes, after a slow turn (left or right) as I apply the brakes there is nothing. Thoughts?

Bad wheel bearings pushing the front pistons back in?

[mnorvold]

Originally Posted by Slagburn

Bad wheel bearings pushing the front pistons back in?

Perhaps, is that really a concern? I will check

[Kilby]

Originally Posted by xjaddiction

I swapped a '92Ford E-350 master cylinder into my MJ (I've got Waggy D-44's under it).

That won't work on stock brakes.

[xjaddiction]

nope

[mnorvold]

Today, after replacing both rear cyls, MC, purging and filling the system with new fluid, setting up the rears, new front hoses i decided to check a suggestion from "Slagburn". He thought maybe it was a faulty wheel bearing pushing the piston in. I wasn't sure that this could happen but I knew that it was in need of replacement so since it had to be done, i did it.....not really thinking that it would help.........by gosh and by golly SLAGBURN WAS RIGHT!. Thanks to all of you for your patience and help

[visa]

how is a wheel bearing pushing the pistion back in? im having the same proablem with the front not having any stopping power but the rear are locking up and no pedle......any one....

[Jam Master Jay]

Wow, old thread. Nobody should complain about people not using the search function here....


If your wheel bearing is worn out and letting the wheel wobble, the rotor will push the pads and thus the piston back into the caliper as it wobbles. That will make it such that the piston has to travel farther to grip the rotor and that's why the pedal is softer or the travel is longer.

FYI In normal operation your brake pads are riding on the rotor. There should be no gap between the caliper and pads or pads and rotor.

[visa]

in that case i dont think thats the problem cause it all new parts, if it helps here is some extra info, its a 94 Yj that i just swapped in some dana 44's from a 89 grand waggy, the only parts that are not new are the calipers and it still has drum rears with all new parts, im thinking that readjusting the rear might help, but there fells like there's nothing in the front and there is a real soft pedle, pumping will only lock up the rear and still fells like it has nothing in the front. i know that all the break components are a bit bigger, but not by much, so could it be an issue of the amount of fluid that has to be pushed through it too......