Mystery brake issue
10-29-2017, 05:09 PM
#1
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Year: 1998
Model: Cherokee
Engine: 4.0
Mystery brake issue
98 XJ. I had a sticky caliper. Started by replacing both front calipers and rotors and bled them. Then, I had almost no braking power at all. Replaced master cylinder, rear wheel cylinders and shoes, as well as rear brake lines, bled all 4 brakes, adjusted rears. Still nothing. Replaced power booster, bled all 4 brakes, still soft. Adjusted rod in power booster. Still soft. No leaking fluid anywhere. WTF?
Last edited by paulutions; 10-29-2017 at 05:30 PM. Reason: Forgot a part
10-29-2017, 05:19 PM
#2
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vacuum hose to the booster leaking ?
marc
edit: does your idle change when pressing the brake pedal ?, did you bench bleed the master cylinder ?
marc
edit: does your idle change when pressing the brake pedal ?, did you bench bleed the master cylinder ?
Last edited by LadyKenai; 10-29-2017 at 05:26 PM.
10-29-2017, 05:32 PM
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Year: 1998
Model: Cherokee
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I replaced the vaccum line. But, yes, the idle does change when I apply the brakes and the break light goes on and off intermittently
10-29-2017, 05:37 PM
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if your idle changes while pressing the brake you have a vacuum leak somewhere
marc
let me rewrite this..
edit: if there is a 'noticable' idle change when pressing the brake and its outside 'specification limits' you are probably looking at a vacuum leak
marc
let me rewrite this..
edit: if there is a 'noticable' idle change when pressing the brake and its outside 'specification limits' you are probably looking at a vacuum leak
Last edited by LadyKenai; 10-31-2017 at 08:12 PM.
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10-29-2017, 11:14 PM
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Year: 1990
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An idle change when pumping the brakes is normal so ignore that. Do make sure that you put the front calipers on the correct sides, bleeders above the hose.
10-29-2017, 11:31 PM
#9
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In my past 3 Jeep's I have never had an idle change when pumping the brakes. That's my solo input. Maybe someone can explain this better to me?
10-30-2017, 08:10 AM
#10
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Um. I feel stupid. Yes, I did put the calipers on the wrong side. I just went by the L & the R that the nice guy at Oreilly's wrote on the boxes & forgot all about it. Thanks for reminding me, y'all. I'll let you know if that's the problem.
10-30-2017, 10:02 AM
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The upside down calipers is your issue. Since the bleeder isn't at the top there's a lot of air in there.
A tip to not loose fluid while swapping calipers: Using a bar or something, there's actually a tool for this too, hold the brake pedal down a bit while doing the work. With the master cylinder pistons pressed away from their normal resting point they block fluid flow. You may have a small amount of pressure so when you open the first bleeder expect a small squirt of fluid, after that you'll have almost no leakage while things are apart. I've had systems open for days and didn't loose any fluid. Be aware that the brake lights will probably be on so if you're gonna have it apart for many hours you might drain your battery.
In the video posted he says the front reservoir for the front brakes, that's backwards. The front reservoir is the rear brakes.
A tip to not loose fluid while swapping calipers: Using a bar or something, there's actually a tool for this too, hold the brake pedal down a bit while doing the work. With the master cylinder pistons pressed away from their normal resting point they block fluid flow. You may have a small amount of pressure so when you open the first bleeder expect a small squirt of fluid, after that you'll have almost no leakage while things are apart. I've had systems open for days and didn't loose any fluid. Be aware that the brake lights will probably be on so if you're gonna have it apart for many hours you might drain your battery.
In the video posted he says the front reservoir for the front brakes, that's backwards. The front reservoir is the rear brakes.
10-30-2017, 05:02 PM
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on 2 of our jeeps the idle doesnt change when i press the brake the other jeep does and i know for fact its the booster is leaking. if you should ignore that? thats up to you
marc
marc