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Unread 08-21-2013, 06:07 AM   #1
Deadhorse
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1997 TJ Wrangler 
 
Join Date: Sep 2003
Location: utica
Posts: 253
Braking issue?

First of all my ABS light has been coming on and off since the day I've had this vehicle but only recently has this been happening. Periodically when applying the brakes it's loosing pressure, for the lack of a better explanation. It is loosing pressure but it's almost like they're fighting it, like they're trying to grab something. Anyway I haven't changed the pads or rotors in a while but when it's breaking ok there's no indication that there any problem there.

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Unread 08-21-2013, 11:35 AM   #2
V65Ozzie
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1998 ZJ 
 
Join Date: Feb 2012
Location: Wilson, nc
Posts: 516
Need a little better info, does the pedal sink to the floor, or does it feel like it's dropping lower and kind of vibrating?

A pedal that sinks to the floor is a sign of a bad master cylinder, this can trigger the ABS pump. A pedal that drops and vibrates indicates the ABS has been activated. There are several scenarios that can cause this, so try to explain as clearly as possible.
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Unread 08-21-2013, 12:05 PM   #3
Oldfrog
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1997 ZJ 
 
Join Date: Feb 2008
Location: Louisiana/Texas
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Do you hear a loud hissing when applying the pedal? If so, you need a new booster.
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Unread 08-21-2013, 12:13 PM   #4
Deadhorse
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1997 TJ Wrangler 
 
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I found it hard to explain when I wrote the thread this morning but it's definitely not sinking to the floor, if anything it's like it's trying to kick it back up but I of course I'm trying to stop so I have to keep pushing down. Not hearing any hissing noise that's for sure.
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Unread 08-21-2013, 12:26 PM   #5
V65Ozzie
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1998 ZJ 
 
Join Date: Feb 2012
Location: Wilson, nc
Posts: 516
Your abs is activating. This can be caused by a few things. A bad sensor(doubtful because your light isn't one all the time) a bad exciter ring(easy enough to check, look carefully for a crack or missing tooth) Bad air gap due to a worn wheel bearing or misadjustment, a finicky connector, probably a couple of other things. Mine does the same thing, I pulled the fuse for the ABS temporarily because it was annoying, and I just deal with the light for now. Mine was fine until I swapped the rear axle assembly, so mine is either a bad sensor, bearing or exciter ring, I'll get around to figuring it out one day. I'm not an expert on Jeep ABS but I have a pretty good understanding of the basics. A full on scanner could tell you which wheel was causing it, but I don't have one, I doubt you do, and I won't pay the dealer 100 bucks to do something that will take them 10 minutes max to figure out.
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Unread 08-21-2013, 12:48 PM   #6
Deadhorse
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Join Date: Sep 2003
Location: utica
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Well I think you know more than the average Joe and now I think about it that's what I feels like, when it wants to slide in the winter and the ABS activates, I'll pull the fuse and just have them take care of it when it's up for inspection in a couple of months.

Thanks so much for your help!

Forgot to ask, where would I look for the crack or missing tooth?
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Unread 08-21-2013, 01:24 PM   #7
V65Ozzie
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1998 ZJ 
 
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Location: Wilson, nc
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Look for the sensors, the ZJ has 4, 1 at each wheel, They stick through the backing plate on the rear, attached to the axle is a metal tone ring(looks almost like a gear) The sensor reads the gaps between the teeth to deterimine the wheel is moving, a missing tooth, cracked ring, bad airgap or worn bearing can fool the system into thinking the wheel has locked up, activating the system, I forget how many times a second it reads, but I want to say between 20-40 times a second for it to refresh the abs computer, so it doesn't take much to trigger it, once triggered it will cycle once and if the system senses wheel speed is restored, shut down. A cycle can take a couple of seconds, which is what you are feeling in the pedal. I assume this only happens when coming to a complete stop, probably between 5-10 mph?
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Unread 08-22-2013, 01:36 AM   #8
jabba974
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1996 ZJ 
 
Join Date: Mar 2013
Location: Ionia, MI
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Mine did that above 20mph.... I had broke the exciter/tone ring which is on the axle/cv shaft...you can see it from the back side where it goes into the wheel bearing...you can replace the tone ring for about $12...also check the sensor that bolts onto the spindle...that could be bad or dirty...
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