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Unread 11-10-2013, 12:30 PM   #1
Dozer105
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1996 ZJ 
 
Join Date: Nov 2013
Location: Richmond Hill, GA
Posts: 3
Newbie Brake Problem

Hello all I am new here on the forum and really could use some help. I have a a 1996 ZJ that I am trying to fix up back to its glory days I have put considerable amount of time and energy into this rig so far. I lifted it 3.5 inches with a Rock Country lift kit put a front stabilizer bar by Rock Country as well. I just finished installing a new rear end as the one that was on it was bent badly and could not be aligned properly at all. I have also spent alot of money and time on the Brake system for this as well I have a brand new Brake Booster, Brand new Master Cylinder, new rotors and pads all the way around the calipers were in great shape no faults found same with ABS components. When I bought the rig it had the brake light on and no stopping power at all so I replaced a lot of components mostly because I wanted it to be new add to the restoration of it. However I just had another Master cylinder installed because when the rear axle was installed yet again the brakes would not bleed and the pedal is weak and sinks to the floor. Now ever with all those new parts including another master cylinder installed it still has very weak pedal I went and bought new brake hoses all the way around but I am at wits end and could really use some help figuring out what is wrong with it because besides myself 3 other mechanics have not been able to fix this brake system fully yet. Any Ideas please after I replace these hoses the system is practically brand new all the way except the ABS Module but there are no codes showing unlike when I bought this Jeep.

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Unread 11-10-2013, 12:40 PM   #2
durango-bob
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2000 TJ Wrangler 
 
Join Date: Jul 2008
Location: Sioux Falls, South Dakota
Posts: 2,826
Sounds like you might have some air in the system. Can you pump it up with the pedal?
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Unread 11-10-2013, 12:58 PM   #3
Dozer105
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1996 ZJ 
 
Join Date: Nov 2013
Location: Richmond Hill, GA
Posts: 3
When the vehicle is off there is pressure but when it is running the pedal sinks. When the brakes were bled there was no air coming out of the bleeder valves. I can stop the vehicle but if I have to slam on brakes forget it it will not stop. one person told me my brake hoses might be inflating that I should try replacing those so I bought new ones all round if this doesn't work I don't know what else it could be. Even the Jeep dealership can't figure this out for me they got the jeep to be able to stop but we still scratching our heads on the pedal feeling so weak ????
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Unread 11-10-2013, 07:59 PM   #4
kachink
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1998 ZJ 
 
Join Date: Sep 2010
Location: Lake Forest, CA
Posts: 497
When durango-bob asked if you could pump it up with the pedal he meant does the pedal get stiffer if you pump it up and down several times. If so, it's a sign of air in the system. You can bleed all 4 wheels clear and still have air elsewhere in the system, especially if you've had the master cylinder off. The DRB scantool that the dealer has even has the ability to cycle the antilock brake valve for the purpose of getting air bubbles to move that may have lodged in there.
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Unread 11-10-2013, 11:42 PM   #5
Dozer105
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1996 ZJ 
 
Join Date: Nov 2013
Location: Richmond Hill, GA
Posts: 3
Quote:
Originally Posted by kachink View Post
When durango-bob asked if you could pump it up with the pedal he meant does the pedal get stiffer if you pump it up and down several times. If so, it's a sign of air in the system. You can bleed all 4 wheels clear and still have air elsewhere in the system, especially if you've had the master cylinder off. The DRB scantool that the dealer has even has the ability to cycle the anti lock brake valve for the purpose of getting air bubbles to move that may have lodged in there.
Yes I understand but no it only has pressure when the vehicle is off when its running there is none I have pumped it over and over again and it just sinks to the floor. I had the Jeep Dealer hook it up and they gave it back the same way it was a little bit stronger that what it initially was but still not correct. When they installed the Master cylinder they even bench bleed it before installing. I am beginning to think that the Brake booster is faulty I replaced it with a new one but today I had another shop tell me they think it was a bad part I received. The part is under warranty so I am going to swap it out once more and see if this might be a vacuum problem as well.
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Unread 11-11-2013, 03:53 AM   #6
Technohead
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1998 ZJ 
 
Join Date: Dec 2008
Location: Exeter, RI
Posts: 6,590
The pads are supposed to slide along the caliper brackets. Sometimes the brackets wear and the pads get stuck -> Will cause the symptom you describe.
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Unread 11-11-2013, 06:13 PM   #7
JasonStebbins
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1997 ZJ 
 
Join Date: Jan 2009
Posts: 3,138
Quote:
Originally Posted by Technohead View Post
The pads are supposed to slide along the caliper brackets. Sometimes the brackets wear and the pads get stuck -> Will cause the symptom you describe.
What Techno means is that if your knuckles have grooves in them where the pads sit, it can cause them to not reach the rotor. Welding will need to be done. Start the Jeep with your foot on the brake, if it sinks after started you have a bad booster or internally leaking master cylinder.
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