Need to pump brakes in order to get pressure - Page 3 - JeepForum.com
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post #31 of 43 Old 02-04-2010, 08:45 AM
Falkon
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Yet a bad caliper alone shouldn't cause the spongy pedal. It's doing the replacement that will introduce air into the lines that will do it.

So unless Vdub opened the system it's doubtful there is air in a line. Most likely a bad MC that's causing the problem. Not the booster. Vacuum has nothing to do w/ it either.


Last edited by Falkon; 02-04-2010 at 12:35 PM.
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post #32 of 43 Old 02-04-2010, 04:50 PM
vdub
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ok im picking up a MC tonight.. prolly gonna bench bleed it and put it in tomorrow.. i never opened the system to introduce air so im guessing my MC just went bad. napa has an MC for $53 with lifetime warranty
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post #33 of 43 Old 02-04-2010, 06:21 PM
khanson
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soft peddel

it could be master cylinder but check for brake fluid leak at all four wheels if you have a leak there will be fluid running down caliper or brake line or inback you will see it running down brake drum to rim and tire that means you have a leak so no press at pedel
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post #34 of 43 Old 02-04-2010, 08:15 PM
Falkon
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Reread the whole post please.
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post #35 of 43 Old 02-04-2010, 09:17 PM
vdub
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No fluid leak anywhere for me or the OP
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post #36 of 43 Old 02-07-2010, 07:35 PM
FortCollinsZJ
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Same issue and symptoms here. I have a very soft pedal that eventually builds pressure but experienced some new issues, today had it in 2 low (front driveshaft out) once the brake pressure was built, the front brakes will lock, but the rears absolutely won't. So being in low range, with the brakes on, the rear wheels just kept pushing me forward, the front tires were just pushing up piles of snow. Definitly the master cylinder failing.
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post #37 of 43 Old 10-02-2010, 10:12 PM
XJWJZX3
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Service Manuals FTW

LOW PEDAL

If a low pedal is experienced, pump the pedal several times. If the pedal comes back up, the most likely causes are worn linings, rotors, or calipers are not sliding on the slide pins.

The proper course of action is to inspect and replace all worn component.
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post #38 of 43 Old 01-24-2013, 11:25 PM
snakeroo
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Okay, after reading thru quite a few threads, I am coming back to this one, as it is most similar to my problem. About 5 days ago, this started. I didn't do any brake work. Last work was entirely new front end(lines, calipers, pads) 3 years ago. When I release the pedal, I think I hear a minor clunking noise from the rear. So far I see no leaks, but maybe it's a bad drum cylinder? If it is bad, will it be obvious when I pull the drum cover off? (visible leakage?). Thanks!

Blue 1993 Wrangler YJ, 6cyl, 4.0L 5spd, 140K miles.
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post #39 of 43 Old 01-25-2013, 08:07 AM
AVR2
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Quote:
Originally Posted by snakeroo View Post
maybe it's a bad drum cylinder? If it is bad, will it be obvious when I pull the drum cover off? (visible leakage?)
Depends how bad it is. I just changed my rear wheel cylinders, and although they were covered in surface rust, there was no obvious leakage... until I'd disassembled the drum assembly enough to pull the two pushrods off either side of the cylinder. Then I could see that the ends of the rods that go into the rubber boots on the cylinder were wet with brake fluid.
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post #40 of 43 Old 12-01-2013, 02:52 PM
shannonandjeeps
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My 98 jeep cherokee has abs breaks its all new partseven lines but ive bleed 1 gallon of fluid I still spongse foot
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post #41 of 43 Old 05-04-2016, 09:32 AM
MT96Cheroke
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Pedal goes all the way to the floor

My daughter bought a 96 Cherokee. Front pads were almost worn out, and she finally asked me to fix it because the pedal was going to the floor and it was hard to stop!
I replaced the front brakes using two remanufactured calipers I had on another 96 Cherokee I own that I use for parts. The calipers were just put on the parts jeep so I pulled them off, disassembled them, cleaned, made sure there was no problems with the caliper pistons, cylinder-walls of the calipers, cleaned everything out, reassembled, perfect, clean, functioning perfectly.
I noticed the brake fluid reservoir was full of black crap, flakey, carbonized **** that can clog the lines. Usually, this condition is caused by the disintegration of the rubber-cup seals in the Master Cylinder (MC). So, I replaced the MC (properly bench bleeding first) and installed a re-man from O’Rielly. (I know, I know, cheesy parts give cheesy service.) Because of the black sludge in the lines, I flushed the lines by opening them at the ABS out ports (3, one for the two rear wheels, and one each for the left and right front brakes). And caliper bleed and wheel cylinder bleeds (rears). Just connect a clear hose to a bottle and squeeze fluid until the fluid clears. Put everything back together bleeding at the lowest points air could get into the system. Which in this case was the ABS pump 3 outgoing lines, and at each wheel in the proper sequence, RR, LR, RF, LF. Still the pedal would pump up, but after 10 seconds, the pedal would travel ALL THE WAY TO THE FLOOR!
Ok, so the master cylinder had to be bad right? I replaced it with a brand new one from NAPA. Bleed everything; still pedal would travel ALL THE WAY TO THE FLOOR!
WTF! Second guessing everything I did. We had the vehicle running and I pulled the vacuum booster hose of the power booster, seemed to firm up the pedal. (of course it does, the primary symptom of a bad booster is the pedal is hard, and takes a lot of pressure to stop because you have no power-assist.)
Replaced the booster, still pedal would travel ALL THE WAY TO THE FLOOR! Arrgh! Now in my 54 years I have done well over 100 brake jobs that included all components of a brake system. Second guessing myself. Ok, it’s got to be in the Brass-Proportioning block, or the ABS system/solenoids right? The proportioning valve appeared perfect. I loosened the 3 out to brake lines on the ABS and jumped the motor by attaching to jumper clips to the battery and then to the ABS power connection. Crack a line, engage the ABS, did this several times clearing any possible air out of the ABS pump, still pedal would travel ALL THE WAY TO THE FLOOR!
By now I’m losing my mind, WTF! Then after a week of doing everything you can imagine to a brake system, I notice the bleed valves on the front calipers are at the “BOTTOM” of the caliper cylinder. I had installed the calipers on the wrong side. Even though the left and right caliper appear identical, the bleed valve must be on top!
The problem was, when I put the calipers back on, I put them on the wrong side. The bleed valves MUST be at the top of the caliper cylinder or air bubbles will settle at the top and you can bleed 5 quarts of Dot-3 through the system and the air will still be there! Swapped the calipers on the front so the bleed valves are on top of the caliper, and IT WORKS PERFECTLY! (After bleeding the fronts again) Nice stiff pedal.
Always look for the SIMPLE things that the most experienced can overlook!
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post #42 of 43 Old 05-23-2016, 02:05 PM
crusher8101
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Wow, MT96! Thanks for that post! I'm no mechanic & often manage to get things fixed by the knowledge shared on this forum, but I screw things up on occasion & get really pissed off with myself. But if a master of brakes like yourself can mount calipers upside down I need to ease up on myself some. I'm sure you were tired or distracted, but the story sure makes me feel better!!
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post #43 of 43 Old 05-23-2016, 02:09 PM
AVR2
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Upside-down calipers are a common issue - they have been discussed here many times. Whenever anyone posts to say that they've changed the calipers and now they can't get the brakes to hold pressure, the first response is always "You've probably got the calipers upside-down"...
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