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Unread 03-15-2015, 02:10 PM   #1
Opeter
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Spongy TJ Brakes!

I have a 2002 Sahara TJ.
The brakes are very soft and spongy. Matter of fact, if you stop hard on the brakes they won't even lock up. The car just gradually stops.
I have bled all the brakes and replaced the old brake fluid with new fluid and that did not help. Can this be a bad Master cylinder or perhaps the power booster?? When depressing the brakes you can hear a suction type noise coming from the power booster. Is that normal? Also, when I was bleeding the brakes, the right rear seemed to have a lot of air. Could it be possible that the wheel cylinder (drum brakes) needs replacing? Any info would be helpful. I'm not very technical when it comes to diagnosing the problem. I'm more mechanical and if someone tells me what needs to be fixed I can fix it!
Thank you:

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Unread 03-15-2015, 02:15 PM   #2
biffgnar
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When you hear that noise, new booster time.
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Unread 03-15-2015, 02:28 PM   #3
Jeepster83
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Sounds like a booster. But check the rubber grommets that are on the booster itself and the intake. It may just be a dried up grommet allowing a vacuum leak. Any idle issues or hvac problems?
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Unread 03-15-2015, 03:04 PM   #4
mrblaine
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Quote:
Originally Posted by biffgnar View Post
When you hear that noise, new booster time.
While he may very well be in need of a new booster, one that is dead or dying will produce the exact opposite problem of a soft and spongy brake pedal.

The lack of assist from the booster make the pedal rock hard with minimal travel typically. That doesn't mean the booster isn't dying, but something else it going on as well.
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Unread 03-16-2015, 08:31 AM   #5
Opeter
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No Vacuum Leaks that I know of. The car was recently "smoked" for a vacuum leak, but that was fixed and there we no other leaks.
Good point about the Opposite affect with a bad booster. I'd hate to swap it out and find the same problem exists. Could it be a bad master cylinder?
Do you guys here a suction noise on your 99 and 03 TJ's when depressing the brake pedal?
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Unread 03-16-2015, 08:39 AM   #6
Jeepster83
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Originally Posted by Opeter View Post
No Vacuum Leaks that I know of. The car was recently "smoked" for a vacuum leak, but that was fixed and there we no other leaks.
Good point about the Opposite affect with a bad booster. I'd hate to swap it out and find the same problem exists. Could it be a bad master cylinder?
Do you guys here a suction noise on your 99 and 03 TJ's when depressing the brake pedal?
Thank you
'03 TJ Sport

No suction noise but a slight hissing sound yes.

Edit: do you have drum or disk brakes in the rear?
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Unread 03-16-2015, 08:46 AM   #7
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Disk or drum in the rear? If drum are they adjusted up? Are all the bleeder screws on top? Do the Brakes 'pump up' and give a good pedal? Does the pedal drop when sitting at a stoplight? If you hold the brake, lightly release it then quickly press the pedal again does it drop?
You can put a clamp on each of the brake hoses then try the brake pedal, if its rock hard, start releasing the clamps one at a time and try the pedal, when it drops you have your source. many will argue this is a bad thing to do (clamping the hoses) and they are correct, however it is the only way to isolate parts of the system for diagnosis.
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Unread 03-16-2015, 09:31 AM   #8
Opeter
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Yes, drum brakes on the back. The sound could be described as "hissing" as opposed to "suction" It is prominent though. Not slight.
Bleeder screws on top, so yes, drum brakes. Pedal does not drop when sitting at a light. It holds true. I took it out yesterday got the speed up to 35-40 and jumped hard on the brakes. No lock up! Just gradual stop. (either front disk or back drum) I don't have hoses on the car, they are all brake lines so I can't clamp them, although a good idea. Perhaps I gotta bite the damn bullet and take it in. hate doing that.
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Unread 03-16-2015, 10:23 AM   #9
mattdoc
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Quote:
Originally Posted by Opeter View Post
I don't have hoses on the car, they are all brake lines so I can't clamp them, although a good idea. Perhaps I gotta bite the damn bullet and take it in. hate doing that.
You have a brake hose from the drivers side frame to the rear axle. And one to each front wheel, in the wheel well.
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Unread 03-16-2015, 10:51 AM   #10
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OH! ok, thanks
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Unread 03-16-2015, 10:56 AM   #11
afusco1222
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The master cylinder could be bypassing internally. That would make the pedal spongy and the fluid level wouldn't change.
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Unread 03-16-2015, 01:27 PM   #12
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Is the reservoir caps gasket swollen up? To the point where it makes it difficult to put the cap on. That would mean the wrong fliud was used and that fluid will eat up the rubber gaskets in the brake system. This will make the brakes spongy and soft.
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Unread 03-16-2015, 03:42 PM   #13
Jeepster83
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Check the condition of the shoes and hardware before you do anything. There's a star wheel down low under the drum and an arm that rests on it. If that arm isn't touching the star then bend it a bit until it does so it can do it's job. Then reinstall the drum and adjust the shoes up until there's very slight drag on the drum and it doesn't spin freely or TOO easily. There's a rubber grommet on the back side of the backing plate down low for you to move that star wheel (take note of which way to turn it to spread the drums apart when you have the drum off). After you do that go drive it on an abandonned road and report back what the result is.

FWIW my TJ has always made the hissing sound and I'm sure it's normal as its not very loud and I have to listen for it. The sound is like fluid passing through a small passage... which is exactly what it is.
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Unread 03-16-2015, 04:12 PM   #14
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Thanks - I'll give that a try this Saturday when I have some free time.
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Unread 03-16-2015, 04:21 PM   #15
Jeepster83
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Thanks - I'll give that a try this Saturday when I have some free time.
Are you driving the vehicle like this every day? If so you're a road hazard and it's not safe for you or others around you on the road. It only takes a few minutes to Jack up and remove the wheels for an inspection.

It may just be time for some new brake shoes and hardware. Possibly get the drums turned or replaced too if necessary.
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