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Unread 06-28-2015, 11:13 PM   #1
Blk92XJGuy
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1992 XJ Cherokee 
 
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Losing brakes/ABS light

Recently lifted the Jeep and could have sworn I double and triple checked everything when I installed it but somehow my drivers lower shock mount bolt broke and my shock was hanging off to the side and was pressing into my caliper in turns. Well after a while my ABS light kicked on, and shortly after my brake pedal went to the floor. I temporarily fixed the shock due to not having time/access to bolts, and went for a test drive and all was well. Well it happened again today. I don't drive this a lot so there's no safety concerns but this needs to be addressed asap. What's causing this? There doesn't appear to be a broken line. There's no puddle or fluid drops under the Jeep.. I want to take this to a shop so it's done right, but I want to know what it is so I'm not taken advantage of. Any ideas?

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Unread 06-29-2015, 01:29 AM   #2
AVR2
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The ABS light is probably down to a sensor problem - the loose shock may have damaged the wiring or the sensor itself.

The brake pedal going to the floor will be a separate issue. The ABS light *only* comes on for issues directly related to the ABS system (the sensors, the computer and the pump), it does not come on for any reason that could be causing the pedal to go to the floor.

If you don't have any fluid leaks and the red brake light is not coming on when you hit the pedal, my guess would be that your brake booster is bad, so you're not getting any power assistance.

BTW, your profile says you have an XJ, and this is the ZJ forum. You may well get better advice in the proper place - click!
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Unread 06-29-2015, 12:40 PM   #3
Blk92XJGuy
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Ah OK. The brake light did come on shortly after the abs light when I lost braking power. Is this something I should give over to a shop or can I reach place it myself? Thanks for the info too! Also this is for my 98 Niner!
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Unread 06-30-2015, 01:43 AM   #4
AVR2
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You can replace the booster yourself, sure. Only real downside is that you have to remove the master cylinder, which means opening the brake lines, which means the tedium of having to bleed them afterwards.
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Unread 06-30-2015, 10:42 AM   #5
Blk92XJGuy
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Could this be heat related? Only asking so I can rule everything out. I have these wheels on the Jeep, and everyone I talked to that runs them haven't had any issues with their Jeeps.

http://i.imgur.com/xcfM2MH.jpg


Also, if I have a known vacuum leak in the Jeep, would that cause any of this?
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Unread 06-30-2015, 02:05 PM   #6
Blk92XJGuy
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Midas quoted me about $430 to replace my master cylinder and bleed the system.
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Unread 06-30-2015, 03:01 PM   #7
zjosh93
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Quote:
Originally Posted by AVR2 View Post
You can replace the booster yourself, sure. Only real downside is that you have to remove the master cylinder, which means opening the brake lines, which means the tedium of having to bleed them afterwards.
On my 93 I was able to loosen the ABS module and pull the master cylinder away from the booster enough to remove and reinstall the booster without opening the lines.

I pulled the booster position sensor out without bleeding the vacuum and it sucked the o-ring inside. Dumb mistake Just had to pull it out and shake it around to get the o-ring out.
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Unread 06-30-2015, 03:23 PM   #8
Blk92XJGuy
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Quote:
Originally Posted by zjosh93 View Post

On my 93 I was able to loosen the ABS module and pull the master cylinder away from the booster enough to remove and reinstall the booster without opening the lines.

I pulled the booster position sensor out without bleeding the vacuum and it sucked the o-ring inside. Dumb mistake Just had to pull it out and shake it around to get the o-ring out.
I don't mind needing to bleed the system since I literally have a brake shop 2 blocks away and I can even tow it. Is it a lot easier to disconnect the lines?
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Unread 06-30-2015, 03:33 PM   #9
zjosh93
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Quote:
Originally Posted by Blk92XJGuy View Post
I don't mind needing to bleed the system since I literally have a brake shop 2 blocks away and I can even tow it. Is it a lot easier to disconnect the lines?
Yes, I just didn't have the new fluid or the time in my case. It's not a hard job either way.
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Unread 06-30-2015, 04:38 PM   #10
Uniblurb
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Quote:
Originally Posted by Blk92XJGuy View Post
Midas quoted me about $430 to replace my master cylinder and bleed the system.
I don't think I'd ever go near Midas again and the one near me is nothing but a rip-off!

Knew I needed a new exhaust about 10 years ago but it just happened to break near their shop. Since pouring rain I had them do the cat back exhaust which cost me an arm and a leg. They said it would sound just like OE but a whole lot louder with their wimpy small cat and shorter than OE muffler.

I had bought their best "Gold" muffler and within 1 1/2 years it was rusted through/leaking. Called since the whole exhaust had their lifetime warranty. Didn't cover labor and they wanted $100+ to install a new muffler which was under warranty.

Said heck with them and 1st & last time I had anybody other than myself touch my exhaust in 19 years! Learned my lesson on Midas.

If you do end up bleeding your brakes and/or installing all new fluid the below Motive Power Bleeder for Chrysler was one of the best tool investments I made 2-3 years ago.

http://www.amazon.com/Motive-Product...r+for+chrysler

Turns brake bleeding into a one man job and a whole lot less bit*hin' than getting the wife involved!
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-Stalling ZJ? 12 things to check before replacing a sensor; the Dirty Dozen
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Unread 06-30-2015, 05:40 PM   #11
Roadtripguy
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Check the ABS sensor wiring VERY closely on the corner that had the loose shock. I had this happen on my 96 Laredo towards the end of last Winter.

Unbeknownst to me, both lower shock bolts were gone in the RF corner, and my shock was rattling around down there when I'd hit a pothole or bump. My ABS light eventually came on, and shortly thereafter, I began to experience an intermittent brake failure (The red "brake" light would come on when this happened), with the brake pedal going to the floor. Then the brake pressure would magically come back!

Long story short: The loose shock wore out the insulation to the ABS sensor wire in one small place. It didn't wear 100% through the wire, but it wore it enough that the internal wires were visible, and frayed. I found I could reproduce the brake failure by turning the steering wheel back and forth in my driveway.

My fix was repairing the frayed ABS sensor wire (which I still need to REPLACE some time this Summer). No more brake failures or trouble lights!

I can't explain why this wire being damaged caused the system to intermittently lose pressure, but in my case, it was 100% of my problem.

I'd put on my microscope eyes, and give that ABS wire a good going over.

YMMV

Good luck!

Quote:
Originally Posted by Blk92XJGuy View Post
Recently lifted the Jeep and could have sworn I double and triple checked everything when I installed it but somehow my drivers lower shock mount bolt broke and my shock was hanging off to the side and was pressing into my caliper in turns. Well after a while my ABS light kicked on, and shortly after my brake pedal went to the floor. I temporarily fixed the shock due to not having time/access to bolts, and went for a test drive and all was well. Well it happened again today. I don't drive this a lot so there's no safety concerns but this needs to be addressed asap. What's causing this? There doesn't appear to be a broken line. There's no puddle or fluid drops under the Jeep.. I want to take this to a shop so it's done right, but I want to know what it is so I'm not taken advantage of. Any ideas?
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Unread 07-01-2015, 07:06 PM   #12
Blk92XJGuy
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Join Date: Jun 2011
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Quote:
Originally Posted by Roadtripguy View Post
Check the ABS sensor wiring VERY closely on the corner that had the loose shock. I had this happen on my 96 Laredo towards the end of last Winter.

Unbeknownst to me, both lower shock bolts were gone in the RF corner, and my shock was rattling around down there when I'd hit a pothole or bump. My ABS light eventually came on, and shortly thereafter, I began to experience an intermittent brake failure (The red "brake" light would come on when this happened), with the brake pedal going to the floor. Then the brake pressure would magically come back!

Long story short: The loose shock wore out the insulation to the ABS sensor wire in one small place. It didn't wear 100% through the wire, but it wore it enough that the internal wires were visible, and frayed. I found I could reproduce the brake failure by turning the steering wheel back and forth in my driveway.

My fix was repairing the frayed ABS sensor wire (which I still need to REPLACE some time this Summer). No more brake failures or trouble lights!

I can't explain why this wire being damaged caused the system to intermittently lose pressure, but in my case, it was 100% of my problem.

I'd put on my microscope eyes, and give that ABS wire a good going over.

YMMV

Good luck!
Wow that looks like it could be my issue. I'll have to find out which wire it is then I'll go give it a really close look. I have a new master cylinder on its way from RockAuto, only $46, so if it is the MC I'll be able to fix it.
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Unread 07-02-2015, 02:59 AM   #13
AVR2
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Quote:
I can't explain why this wire being damaged caused the system to intermittently lose pressure
There's no reason at all that I can see. If the ABS light is on, the system is disabled. Only the ABS hydraulic unit could have any effect on fluid pressure, and then only when the pump was actually running - which obviously only happens if the ABS is triggered during braking, which can't happen if the light is on.
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Unread 07-13-2015, 06:34 PM   #14
Blk92XJGuy
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Quote:
Originally Posted by AVR2 View Post
There's no reason at all that I can see. If the ABS light is on, the system is disabled. Only the ABS hydraulic unit could have any effect on fluid pressure, and then only when the pump was actually running - which obviously only happens if the ABS is triggered during braking, which can't happen if the light is on.
Do you have an idea of what I should look at/for? I didn't really see anything out of the ordinary.
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Unread 07-13-2015, 08:13 PM   #15
Roadtripguy
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I don't know if you want to test my theory, or if you think I'm crazy... But if you want to, the easiest way to do it is to disconnect the ABS sensor pigtail to the corner that had the loose shock, and see if your brake pressure problem magically goes away. You'll still have an ABS light, but you shouldn't get the red "brake" light, or a loss of pedal pressure. That wire could have been stretched out by the loose shock rattling around, and internally damaged, making it so that visually, everything looks okay.

I know my story defies logic, but it happened exactly as I explained it.
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