spongey brakes but unlikely air in lines? - JeepForum.com
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post #1 of 26 Old 08-22-2017, 09:56 PM Thread Starter
TinkerAB
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spongey brakes but unlikely air in lines?

Need the jeep geniuses guidance.

Working on my 01 wrangler. Few months back I swapped in a tj dana 44 rear that had factory discs on it. Installed new centric rotors black magic pads as well as full flush of fluid. Brakes improved but fronts were still bad so not great.

Few days ago I swap in a high pinion 30. I put in brand new rotors and pads and reused the TJ calipers so I wouldn't have to mess with the fluid. As soon as I go to drive it the brakes are spongey as hell. Spongey usually means air in lines so I bleed it and still no good. I then take it to a shop and have it power bled. Still no good. Check valve seems fine. With engine off I can build pressure but as soon as i start engine it goes away.

Only thing I can think of is that by dumb luck my master cylinder went out at the same time I swapped the axle. Any and all ideas are appreciated. thanks.


01 TJ | D44 | HP30 | ARB | 4.88 | 35s
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post #2 of 26 Old 08-22-2017, 10:31 PM
Shark_13
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What year was the new front axle from? There was a change (99-2000 ish?? I can't remember for sure) where different unit bearings and different rotors won't work together.
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post #3 of 26 Old 08-22-2017, 10:34 PM Thread Starter
TinkerAB
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Half way through 99 they changed the rotors. I do have the correct rotors though.

01 TJ | D44 | HP30 | ARB | 4.88 | 35s
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post #4 of 26 Old 08-23-2017, 12:37 AM
Mousejockey
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Are the calipers on the correct side? Bleeders above inlet line?
Check your knuckles for groves/divots where the pads slide. If the pad is stuck in one of these notches, it will flex which will give the feel of a spongy pedal.

This method isn't recommended due to possible damage to the brake hoses but can help, Clamp off the 4 brake lines and see if the pedal is solid, if it isn't then the issue is in the master/booster/ABS, if it is release the clamps one at a time and recheck the pedal, then reattach the clamp and move to the next one. this will isolate the issue.
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post #5 of 26 Old 08-23-2017, 03:44 AM
olysteve
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Are the flex hoses the old rubber type or are they the braided kind? The rubber ones can baloon a bit once they get old and make for soft pedal

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post #6 of 26 Old 08-23-2017, 06:54 AM
mrblaine
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Quote:
Originally Posted by TinkerAB View Post
Need the jeep geniuses guidance.

Working on my 01 wrangler. Few months back I swapped in a tj dana 44 rear that had factory discs on it. Installed new centric rotors black magic pads as well as full flush of fluid. Brakes improved but fronts were still bad so not great.

Few days ago I swap in a high pinion 30. I put in brand new rotors and pads and reused the TJ calipers so I wouldn't have to mess with the fluid. As soon as I go to drive it the brakes are spongey as hell. Spongey usually means air in lines so I bleed it and still no good. I then take it to a shop and have it power bled. Still no good. Check valve seems fine. With engine off I can build pressure but as soon as i start engine it goes away.

Only thing I can think of is that by dumb luck my master cylinder went out at the same time I swapped the axle. Any and all ideas are appreciated. thanks.
Did you disconnect the calipers?

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post #7 of 26 Old 08-23-2017, 08:00 AM Thread Starter
TinkerAB
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Original flex hoses and calipers were not disconnected. Mouse jockey may be onto something with the knuckles. I did notice little notches in the knuckles when putting the brakes together but I didn't really think anything of it. Will investigate that further after work.

01 TJ | D44 | HP30 | ARB | 4.88 | 35s
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post #8 of 26 Old 08-23-2017, 08:04 AM
mrblaine
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Original flex hoses and calipers were not disconnected. Mouse jockey may be onto something with the knuckles. I did notice little notches in the knuckles when putting the brakes together but I didn't really think anything of it. Will investigate that further after work.
Notches won't cause your problem. Take the parking brake off and see if the brake light on the dash is on. When you bled the system, how did you do it?

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post #9 of 26 Old 08-23-2017, 08:13 AM Thread Starter
TinkerAB
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Brake light is not on. Gravity bleed them the same way I have dozens of times and mc never got too low on fluid. RR LR RF LF. But after that I questioned my work and had it done at a very well known shop and they said no air was in the lines and there was no improvement.

01 TJ | D44 | HP30 | ARB | 4.88 | 35s
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post #10 of 26 Old 08-23-2017, 08:21 AM
mrblaine
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Brake light is not on. Gravity bleed them the same way I have dozens of times and mc never got too low on fluid. RR LR RF LF. But after that I questioned my work and had it done at a very well known shop and they said no air was in the lines and there was no improvement.
I've bled hundreds of TJs and have never been able to make gravity bleeding work. The shop may have said there is no air in the lines but there is air in the system somewhere. You have the classic indicator, hard pedal with engine off, drops about half way or more with light pressure on the pedal when you start it.

If you did a manual bleed at each corner with an enthusiastic helper working the pedal, you can judge the health of the system by the rate of fluid movement.

BTW- well known or not, your shop sucks.
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post #11 of 26 Old 08-23-2017, 08:29 AM Thread Starter
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They use a large machine to do it. I guess I can go back in today and have them do it again. I just have doubts it's air as I never even disconnected the calipers when I first put the axle in. Was driving around for 2 months with a solid pedal. So how did air get in the lines while swapping the diff if calipers were never changed.

01 TJ | D44 | HP30 | ARB | 4.88 | 35s
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post #12 of 26 Old 08-23-2017, 08:48 AM
mrblaine
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They use a large machine to do it. I guess I can go back in today and have them do it again. I just have doubts it's air as I never even disconnected the calipers when I first put the axle in. Was driving around for 2 months with a solid pedal. So how did air get in the lines while swapping the diff if calipers were never changed.
A few ways. If the pistons being compressed shoved some debris into the combo valve and contaminated the bore for the safety, then the gravity bleed would drain one end without a full refill of the lines if the valve isn't functioning correctly.

The master may be defective enough to suck in air on the return stroke but not defective enough to have a dropping pedal under moderate pressure.

You did let the master get low enough to need bench bleeding and didn't catch it.

You have a leak you can't see that is also letting air in.

BTW- I have the large machine and I quit using it because it didn't work as well as a proper manual bleed.

You need to verify that the switch on the side of the combo block is capable of tripping the dash light. All you have to do is remove the switch from the side of the block, move it over beside the hole and push the plunger in on the side of the block and have someone watch the dash light with the parking brake handle down.

Once we know that works, we can move onto other things.
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post #13 of 26 Old 08-23-2017, 10:50 AM Thread Starter
TinkerAB
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On my way to work I decided to slam the brakes and see what happened. First time no tires would lock up. Second time front driver wheel locked up. Now it's pulling to the right. Something isn't right with the passenger front brake. Will look at that over after work and make sure the light activates.
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01 TJ | D44 | HP30 | ARB | 4.88 | 35s
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post #14 of 26 Old 08-23-2017, 07:44 PM Thread Starter
TinkerAB
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So on the way home from work I noticed the front right brake was definitely not right. Half way home the brake light comes on the dash. Pull into a parts store. Fluid is still full. Buy a new front right caliper. One the way from parts store to home brake light does not turn on. Get home weld and grind the knuckle so that's fixed. Install new caliper. Rebleed. Haven't really drove it much but just around the block the pedal still isn't right.

01 TJ | D44 | HP30 | ARB | 4.88 | 35s
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post #15 of 26 Old 08-23-2017, 08:35 PM
Shark_13
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I'd follow mrblaine's advice above as far as troubleshooting instead of throwing parts at it.
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