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Unread 09-05-2012, 08:41 PM   #1
shalezzz
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1997 ZJ 
 
Join Date: Aug 2012
Location: Bensalem, PA
Posts: 33
Brake booster problem on zj

Just recently bought a 97 zj i6 disc all around and the brake pedal is hard as a rock and takes more effort than it should to stop. However it does stop.
The check valve works. The line leading to the check valve works.
When I pump the brake to release the vacuum and start the engine with my foot on the pedal, the pedal does drop slightly. The pedal makes a woosh as I press it but does not continue after the initial press.
The only test I haven't done is take a vac gauge to the line.
Theres nice pedal travel at idle in stop and go traffic.

My question is if the brake booster is at fault could it still hold vacuum and work slighty? Or are there other problems that could lead to this thanks

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Unread 09-06-2012, 06:56 PM   #2
jnicewan
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1995 ZJ 
 
Join Date: Dec 2010
Location: Norman, OK
Posts: 2,006
Yes the booster can still hold a vacuum and work slightly or not at all. The diaphragm could be torn or have a hole in it and when you press the pedal the atmospheric valve releases vacuum on one side of the booster but since the diaphragm is faulty you will have no or low assist, basically its just making a vacuum leak when pressing the pedal.
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Unread 09-07-2012, 02:47 PM   #3
shalezzz
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1997 ZJ 
 
Join Date: Aug 2012
Location: Bensalem, PA
Posts: 33
Thanks any expierence with replacemtent brake boosters? I don't know if I should get one from the junkyard and hope it works or buy an a1 cardone vs crown vs omix-ada
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Unread 01-15-2014, 01:08 AM   #4
shalezzz
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1997 ZJ 
 
Join Date: Aug 2012
Location: Bensalem, PA
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UPDATE: replaced pads and booster braking effort is reduced greatly.
however at idle i still have to keep my foot sorta hard on the brake to prevent it from rolling away. harder then what i would prefer. i think i have to do a vac test at idle idk?
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Unread 01-15-2014, 02:01 AM   #5
Uniblurb
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1996 ZJ 
 
Join Date: Jan 2012
Location: Central, Ohio
Posts: 3,213
So have you tested the brake booster rubber grommet where the intake hose attaches to make sure it isn't leaking? When I just turned it out of the way when installing a new header when I turned it back to the correct position it leaked. Know another this same thing happened to and RTV around the grommet where it goes into the metal housing solved the problem.
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-Stalling ZJ? 12 things to check before replacing a sensor; the Dirty Dozen
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Unread 01-16-2014, 03:14 PM   #6
shalezzz
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1997 ZJ 
 
Join Date: Aug 2012
Location: Bensalem, PA
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It's a brand new booster but I'll check and I'll have to check on the intake mani
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