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Unread 10-10-2009, 11:43 AM   #1
Abyx
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1991 XJ Cherokee 
 
Join Date: Oct 2009
Location: New Jersey
Posts: 31
Bendix 9 ABS woes

Hello,

Disclaimer:
I've been rather hesitant to post on this forum for awhile because I've been attempting to solve the problems myself..but I'm extremely new to working on cars and I just can't seem to figure out what's wrong. Keep in mind I really don't know what I'm talking about, I'm trying to learn.

Patchy information:
I have a '91 Cherokee Limited, I bought it back in August and it's my first vehicle..I paid a little over a grand for a half way rebuilt vehicle that's been absolutely fantastic since I bought it, despite the 211xxx miles on the body.

Most of the major components on the vehicle have been replaced with the exception of the transmission(AW-4 I think..) which still works flawlessly. I haven't needed to worry about anything as long as I've kept up the maintenance on it(which I've been doing and learning about as I've gone along.)

However, my current problem just..stumps me. I don't 'know' what is wrong, I don't 'know' why this retarded system is doing what it is. I've scoured the internet in search of answers, several searches on this forum has led me to believe you guys know what you're doing so I figured I'd ask here.

I unfortunately have the Bendix 9 ABS system in my jeep, the previous owner told me that he's had problems with the system in the past and through his personal tests, concluded that the wiring harness needs to be redone and the system components are fine. This led him to zip tie the wires all over the place in an..interesting way that somehow made it work.

Now, that's fine..and I haven't had too much trouble with the system up until recently. Due to an elementary mistake..I was forced to slam on the brakes at a stoplight. By slam, I mean stand on the peddle, slam.


Problem:
Since then, the ABS system has been driving me bonkers, it's just...it's broken! I don't know what's wrong with it! I'm not sure what does what and what goes on where; what wires do what and how they get to where they need to go.

Before this incident, every time I would push on the brakes, they would:

A: Feel very stiff and as my mechanic friend has described as 'spongy'.
B: The mechanism that's attached to that strange plate on the opposite side of the driver's side whines with every push of the peddle. I've come to understand that this machine is some kind of pump that I'm assuming compresses gas to assist in power braking.

Now, since then, the ABS system seems to have developed intelligence, as it activates and deactivates at will and causes my truck to either steer to the left when braking, or just not work, or make weird noises and make my peddle shake.

When it turns off, the ABS light comes on and my brakes work perfectly fine. The machine still whines at varying degrees of peddle pressure. However, the peddle is reasonably stiff and the brakes work fairly well for my uses.

When it turns on...
A: I've read that the ABS system causes your peddle to move violently when it's in use..if that's the case, my peddle moves every time I brake and my jeep jerks around as it comes to a stop.
B: Sometimes when I push on the peddle, I don't get any movement in the peddle..but I hear a strange sound coming from the dashboard where the electrical connections for the brake lines are situated...it sounds like a whining or electrical arching. I'm hesitant to tear apart the lines looking for a frayed wire, but if that's the problem...
C: I'll push on the peddle and the ABS works perfectly fine, it noticeably disengages at speeds below 10mph and my wheels lock up. I've read it's supposed to do that..but it didn't do that before.
E: The system makes strange noises and my jeep veers to the left.

What I've done so far is basically fiddle with everything..it's not too much, but it's what I've been able to think of short of replacing the system. My problem is, I have to fix things on my jeep gradually as I'm not made of money; and I don't even know what I can do to fix this.

I've...
A: Messed with the wires
B: Tried to visually understand the system, and try and see what's messed up(Found a few things like brake fluid on some of the wire connectors..)
C: I've cleaned the wheel sensors(at one point the front left sensor wasn't magnetic, after I cleaned it, it grabbed onto the rotor.
D: Depressurized the system by pumping the brakes x50+ times and letting the motor recharge itself; this often makes a few of the problems go away for a little bit.
E: Simply pulled the fuses out from underneath the dash. This disables my ABS, but it also disables my power brakes leaving me with very soft brakes that don't do much to stop the vehicle.

Doing these few things has improved the problem, but it's still a problem.

If anyone can help me and needs any more information/pictures, just let me know what I can do to help you help me. This is really annoying me because sometimes I don't need to worry about it too much(The ABS turns off) and sometimes I do(the ABS DOESN'T turn off).

Thanks a ton.


P.S. This is especially frustrating because most people have trouble getting their cars to run; mine sprints and doesn't stop! Haha

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Unread 10-10-2009, 12:45 PM   #2
Holder350
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1995 XJ Cherokee 
 
Join Date: Oct 2007
Location: Whitesburg, Tennessee
Posts: 5,290
Remove the Bendix ABS system, its of no use to you anyway.

You do not need to remove the pump, proportioning valve or change master cylinders.

Step #1 Remove all fuses (in the PDC and interior fuse box)
Step #2 Remove all relays (in PDC)

Be happy with a good working non ABS brake system.
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95' XJ Country - Stock Skids - D30/D35 Limited Slip - 3" Lift - 31x10.50R15 - 4.0 HO - AX15 - NP231

98' XJ Classic - D30/C8.25 - 4.5" RC Lift - 33x12.50R15 - 4.0 HO - AW4 - NP231
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You can tell the character of a person in how they treat someone who can do nothing for them.
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Unread 10-10-2009, 05:18 PM   #3
RBxj
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1996 XJ Cherokee 
 
Join Date: Sep 2007
Location: Buckley, WA
Posts: 390
You may want to search XJ booster upgrade, after I disconnected the fuses wiring harnes etc on my Bendix 9 the thing would hardly stop, like no power brakes at all even standing on the pedal at low speeds. I am in the proces of the upgrade now.
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Unread 10-10-2009, 06:16 PM   #4
Holder350
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1995 XJ Cherokee 
 
Join Date: Oct 2007
Location: Whitesburg, Tennessee
Posts: 5,290
Yeah agreed, a 95+ XJ has the double diaphragm booster, so any XJ 95+ is a great swap.

ZJ boosters are also double diaphragm but I'm not sure what years.
__________________
95' XJ Country - Stock Skids - D30/D35 Limited Slip - 3" Lift - 31x10.50R15 - 4.0 HO - AX15 - NP231

98' XJ Classic - D30/C8.25 - 4.5" RC Lift - 33x12.50R15 - 4.0 HO - AW4 - NP231
Quote:
Originally Posted by Azzy View Post
You can tell the character of a person in how they treat someone who can do nothing for them.
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Unread 10-13-2009, 06:52 PM   #5
Abyx
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1991 XJ Cherokee 
 
Join Date: Oct 2009
Location: New Jersey
Posts: 31
I feel preeeetty dumb, but my problem was solved pretty easily.

Removing the fuses from the PDC and under the dash did not fix the problem. It did exactly what I suspected it would - disabled all ABS components and therefor disabled my power brakes..leaving me with braking that would not lock the wheels even at speeds below 5mph.

However, I took a look at the diagram in the PDC and discovered the fuse for the ABS Computer. I decided to yank just that one, and I discovered my ABS system wont turn on. This leaves the components to run by direction of my foot; which provides me with stopping power and no anti-locking.

I'll look into upgrading the booster in the future, but for now my brakes function safely.

Thanks a lot for the help guys! All I needed was to be pointed in the direction of the PDC.
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