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post #1 of (permalink) Old 03-09-2001, 06:19 PM
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brake problem

I just pressed the brake and instead of getting resistance like usual, it snapped and my foot sank down to the bottom. There is a little resistance at the bottom, barely enough to stop the car. The smaller reservoir in the master cylinder was low even though I had recently checked it. I filled it and there was no change in braking. I also found no leaks. Any ideas? THanks. Steve

Steve H. '82 CJ8 258. TR upgrade. Borgeson steering shaft.
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post #2 of (permalink) Old 03-09-2001, 06:54 PM
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Re: brake problem

Did you just do some brake work. I wonder if the system needs to be filled and then bleed off. Worth a try. First check all over for any leaks.

I am not a brake expert, done a few and thats what I would check.


76 CJ5 304 "its a JEEP thing, I hope you understand"
post #3 of (permalink) Old 03-09-2001, 09:02 PM
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Re: brake problem

Sounds like you lost your master cylinder. I can't think of anyhting else.

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post #4 of (permalink) Old 03-09-2001, 09:54 PM
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Re: brake problem

Definitely sounds like the master cylinder. Try bleeding the master cylinder. If not check the prop valve. That happened to me in my Camino and it sounds the same. Good luck!!

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post #5 of (permalink) Old 03-09-2001, 10:16 PM
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Re: brake problem

From most indicators the problem does seem centered in the Master Cylinder. However, that would not equate with the low fluid in the smaller resivour. When a Master Cylinder fails, it's usally from cuts in the seals caused by impurities in the break fluid, or from failing seals due to just plain old age. In both cases the failure is over time, a gradual build up to the day the breaks fail. The sudden failure makes me think of other things rather than strictly a Master Cylinder failure.

You said you checked for leaks. I presume you checked:

a. The Caliper pistions
b. Rear wheel cylinders for weepage.
c. All along the brake lines for evidence of leaks.

Bleed the breaks properly and keep the resivour full during the process and then check the Master Cylinder... I'm bettin' the problem's in the lines or the wheel caliper or rear cylinder assemblies.

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post #6 of (permalink) Old 03-10-2001, 02:04 PM
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Re: brake problem

Here's something else I noticed. I think this might shed some light.

Looking into the master cylinder, it has two chambers. The seal on the lid normally has two corresponding squares on it where the rubber is sort of folded inside itself. One folded area for each chamber. When I opened the lid, one of the folded seals was pushed out and expanded into the chamber, almost like it had been sucked downward. This was the chamber with low fluid, the smaller chamber.

I probably didn't check for leaks thoroughly enough. I just checked the lines from the master cylinder to each wheel.

Sorry for holding out on these little tidbits. Does this change or bolster anyone's opinion? Steve

Steve H. '82 CJ8 258. TR upgrade. Borgeson steering shaft.
post #7 of (permalink) Old 03-10-2001, 05:54 PM
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Re: brake problem

The smaller reservoir is for your rear brakes. I would start from the rear and work your way froward checking for leaks. Start with the wheel cylinders in the rear and trace the lines forward.

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post #8 of (permalink) Old 03-10-2001, 08:34 PM
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Re: brake problem

hey steve.. if it was me, the first thing i'd do is look up inside of the rear wheels, and look for any signs of fluid. follow the lines from the wheels, over the axle, and up toward the front. if no fluid detected, i'd take off the rear wheels and drums one at a time, and check for fluid or parts failure. the last post is right about the small reservoir feeding the rear brakes. you said you lost pedal all at once, that would be either a major leak or parts failure inside the drum, allowing the wheel cylinder to extend too far. you didnt say if you had power brakes. on occassion a failure with the vacuum boost will cause a low pedal. dave

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post #9 of (permalink) Old 03-10-2001, 08:50 PM
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Re: brake problem

I say it's gotta be leaking somewhere. I'd fill the master up and have somebody pump the brakes. If it is leaking you shoud find it faster, unless it's a caliper or wheel cylinder. If it is a caliper or cylinder, it won't be long and you'll see fluid running down the inside of a tire.

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