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Rear brake issue...

hillbilly_jeeper

hillbilly_jeeper

NAXJA Member #1081
Location
Alta, CA
First, the important info. 93, 8.25, 32" tires, rear drums, small drums, non ABS.
No matter what ive tryed, i have not been able to get my rear brakes working right. Out of preventitive maintance, when i got it, i put front pads and rear shoes on it, cleaned everything up, anti-seazed the adjusters, and whatnot. My rears arent really working. Backing down hill, expecially muddy, the font will lock up, but no matter how hard i press the peddle, no rears. Ive adjusted them up till i can feel them dragging, still no go. I thoght maybe master cyclinder or prop. valve. But, tongiht, i was trying to get me parking brake to work, put in YJ cables. I have it adjusted so tight that is take two hands to pull it all the way up....And in neutral on a hill, it will still roll backwards. Im sure i could adjust it more, but im not stong enough to pull the handle!! Im at a loss. probable something simple im missing, but ive done dozens of brake jobs, with no issues. Any ideas??
 
Back the emergency brake cable adjustment off all the way,then adjust the rear brakes.
Tighten the equalizer bar until the brakes hold,the E-brake handle should make 5-7 clicks when adjusted correctly.
Wayne
 
Are you concerned more about the rear brakes when driving, or the parking brake? This is important, because the advice will be different.

It sounds like your big concern is the parking brake, so the answer to that is ... park facing downhill.

Seriously. The rear drum brake setup used on the XJ (and on probably every drum brake system built in American for the last 70 years or so) is what's called a "servo assist" system. Take a look at the shoes, and the locations of the pins and levers. The system is designed so that, when moving forward, once the shoes make contact with the drums and start to rotate, the rotation acts to increase the pressure of the shoes against the drums.

This does not happen in reverse. In general, it is not possible to make the parking brake be effective in reverse without adjusting things so tight that the brakes will be dragging when you drive. This is not a defect of the XJ ... this is a characteristic of drum brake systems.
 
Wayne Sihler said:
Back the emergency brake cable adjustment off all the way,then adjust the rear brakes.
Tighten the equalizer bar until the brakes hold,the E-brake handle should make 5-7 clicks when adjusted correctly.
Wayne
Click to expand...

When i adjusted the rear brakes, the e-brake cables were slack. like i said, It takes 2 hands to pull the e-brake handle all the way up, and even at that, it just rolls through it.
 
Well, im really concerned about making my rear brakes work period. And yes, the parking brake does work...barely, in forward. Ive just never seen it requre so much of a stong pull to get barely nothing. even forwards, if the hill is steep, it will roll thorugh it. Im used to being ablt to set my parking brake, and not be able to drive through it forwar,a t least, and usualy, reverese.
I posed both questions, because im beggining to wonder if there somehow related.
 
Did you have the drums turned when you did the brakes? Are they still within tollerances or are they to thin now. I dont know if this would really cause the problem but just a thought.
 
Check and make sure you´ve got the long shoes on the rear. Make sure you don´t have two shorts on one side and two longs on the other.
New shoes with old drums don´t fit well, it´s advisable to arch the shoes to the drums and/or turn the drums and then arch the shoes to the drum. The new shoes kind of ride on a crown for awhile and often don´t work well until broken in.
It takes months for new shoes to wear and seat into old drums. I´ve found sanding the shoes and drums with 100 grit coated sand paper, helps the process. Also doesn´t hurt to periodically sand the shoes and drums at yearly service intervals.
New shoes, when used to much when new, can glaze and don´t really work at peak.
I think it´s possible to put the parking brake link in backwords (maybe).
A leaky axle seal can cover everything in a coat of 90 wieght oil. A leaky wheel cylinder can cover everything in brake fluid, but the brake fluid actually often makes the brakes grab and lock up.
Most of my tips are for the Renix XJ, but I imagine the newer set up is nearly the same as the old, at least in the basics. Same functions, with a slightly different configuration.
Out of the hundreds (or more) of brake jobs I´ve done, I´ve screwed up few. I didn´t get the brake hold down spring cap seated exactly and it popped off during driving. This caused a chain reaction that pretty much destroyed everything on that side, including the drum. Another was not hooking up the return spring completely on the anchot pin. This caused uneven braking and eventually some noise, but really didn´t do much damage.
I´ve installed new shoes on old unturned drums and after an inspection weeks later, saw where only about 30% of the shoe was actually contacting the drum.
I tried once to put the long and short shoes on the wrong sides, but caught myself in time.
 
Last edited:
8Mud said:
Check and make sure you´ve got the long shoes on the rear. Make sure you don´t have two shorts on one side and two longs on the other.
New shoes with old drums don´t fit well, it´s advisable to arch the shoes to the drums and/or turn the drums and then arch the shoes to the drum. The new shoes kind of ride on a crown for awhile and often don´t work well until broken in.
It takes months for new shoes to wear and seat into old drums. I´ve found sanding the shoes and drums with 100 grit coated sand paper, helps the process. Also doesn´t hurt to periodically sand the shoes and drums at yearly service intervals.
New shoes, when used to much when new, can glaze and don´t really work at peak.
I think it´s possible to put the parking brake link in backwords (maybe).
A leaky axle seal can cover everything in a coat of 90 wieght oil. A leaky wheel cylinder can cover everything in brake fluid, but the brake fluid actually often makes the brakes grab and lock up.
Most of my tips are for the Renix XJ, but I imagine the newer set up is nearly the same as the old, at least in the basics. Same functions, with a slightly different configuration.
Out of the hundreds (or more) of brake jobs I´ve done, I´ve screwed up few. I didn´t get the brake hold down spring cap seated exactly and it popped off during driving. This caused a chain reaction that pretty much destroyed everything on that side, including the drum. Another was not hooking up the return spring completely on the anchot pin. This caused uneven braking and eventually some noise, but really didn´t do much damage.
I´ve installed new shoes on old unturned drums and after an inspection weeks later, saw where only about 30% of the shoe was actually contacting the drum.
I tried once to put the long and short shoes on the wrong sides, but caught myself in time.
Click to expand...
I'll check the long/short shoe thing, but as far as i can recall, they were all the exact same. My axle seals are not leaking. I thought about glazed shoes. They probably have around 5000 miles on them. And the rears have never worked, since day one. Even before i put the new shoes in, the rears and parking brake didnt work. I do know that my drums really need to be turned or replaced. But ive run alot worse drums, and the brakes still at least worked. Guess im gonna have to tear back into it, for further inspection.
Thanks for the help.
 
hillbilly_jeeper said:
I'll check the long/short shoe thing, but as far as i can recall, they were all the exact same. My axle seals are not leaking. I thought about glazed shoes. They probably have around 5000 miles on them. And the rears have never worked, since day one. Even before i put the new shoes in, the rears and parking brake didnt work. I do know that my drums really need to be turned or replaced. But ive run alot worse drums, and the brakes still at least worked. Guess im gonna have to tear back into it, for further inspection.
Thanks for the help.
Click to expand...

SOmebody should tell you that XJ proportional valves (located in small manifold below master cylinder) can goo-up and prevent much if any pressure from reaching the rear system. There is even a modification some XJer's do that provides more rears pressure than working stock unit. I haven't seen that mod in a while but it's somewhere, I'm sure. Easy thing is to clean proportional valve and re-bleed the system.
 
XJXJ said:
SOmebody should tell you that XJ proportional valves (located in small manifold below master cylinder) can goo-up and prevent much if any pressure from reaching the rear system. There is even a modification some XJer's do that provides more rears pressure than working stock unit. I haven't seen that mod in a while but it's somewhere, I'm sure. Easy thing is to clean proportional valve and re-bleed the system.
Click to expand...

I acctual figured it was the proportioning valve all along, untill i started messing with the e-brake. since im having trouble getting either to work, im guessing somethine else. Gonna tear it apart, for the 3rd time, this afternoon, and look into it. IT really sucks trying to back down a muddy hill with no rear brakes.
 
I understand what you are saying about the PARKING brake so of course check your work inside the drums carefully. But, you also wouldn't have the 1st XJ with rusted/stuck cables. After rebuilding my brakes, I raised the rear and noticed they weren't stopping the rear wheels when applied. That took me to the proportional valve. Cleaning the valve and bleeding corrected that problem.
 
XJXJ said:
I understand what you are saying about the PARKING brake so of course check your work inside the drums carefully. But, you also wouldn't have the 1st XJ with rusted/stuck cables. After rebuilding my brakes, I raised the rear and noticed they weren't stopping the rear wheels when applied. That took me to the proportional valve. Cleaning the valve and bleeding corrected that problem.
Click to expand...

Well, cables are brand new YJ cables. SO it is possible to get the prop. valve cleaned? i was under the impression it wasent servaceable, and Napa told my its a dealer only item.
 
Dunno what you mean by YJ cables but it took me a while to understand what e-brake meant too. My problem was that the parking brake worked fine but no or little hydraulic action.

The valve is very simple and contains a threaded rod, seal and spring. It comes right out the front of the brake line manifold. I R&R'd it and bled the brakes. Everything good after that.

I'm 99% sure there is/was a difference between front/rear shoes on the rear of my system. I think mine were 10" x 1-7/8" brakes and I know there are other sizes so make sure you got the right parts and the fitment is correct.
 
XJXJ said:
Dunno what you mean by YJ cables but it took me a while to understand what e-brake meant too. My problem was that the parking brake worked fine but no or little hydraulic action.

The valve is very simple and contains a threaded rod, seal and spring. It comes right out the front of the brake line manifold. I R&R'd it and bled the brakes. Everything good after that.

I'm 99% sure there is/was a difference between front/rear shoes on the rear of my system. I think mine were 10" x 1-7/8" brakes and I know there are other sizes so make sure you got the right parts and the fitment is correct.
Click to expand...

YJ cables are wrangler parking brake cables, because there longer than stock, to account for lift.
I guess im pretty much down to tearing it apart again. Gonna look into the prop. valve, and check the differnt lenght shoe issue. I think there were 9" anmd 10" brakes. Since mine are nine, i dont think the others would fit...made that mistake when i first bought them..first set was too big. Thanks for the advice
 
ALSO, what kind of condition are the soft lines in back there, when they start to get old they expand and do not supply the brake cylinder with adequate oomph.
When you bleed the rear brakes does any fluid come out ?
The hand brake not being able to tighten them up is puzzling. Thats a mechanical function that should work w/no issues.
 
RichP said:
ALSO, what kind of condition are the soft lines in back there, when they start to get old they expand and do not supply the brake cylinder with adequate oomph.
When you bleed the rear brakes does any fluid come out ?
The hand brake not being able to tighten them up is puzzling. Thats a mechanical function that should work w/no issues.
Click to expand...

Yes, fluid comes out of the lines when i bleed them, and i replaced the rubber line when i did my lift. im thinking something mechanical. Im getting ready to go tear into it again, if the rain holds out.
 
Dont know if its gonna completly solve my issues, but i found, that i, stupidly, did have the both long shoes on one side, and both shorts on the other. every other brake job ive done, the shoe frame itself was differnt front to back. on my jeep all 4 look the same, but the linning is diffent. Guess now i know. Now to see is it solves or at least helps me problem!! I would have never noticed, either, Thanks!!
 
Well, i swapped shoes out right, and re-adjusted my brakes, and aside from still being alittling out of adjustment, everything is working! Thanks for the help and replys. Probably never woulda figured that one out.
Note to everyone else out there doing rear brakes....Pay attention to the long and short shoes!!!
 
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