I need a sanity check please - JeepForum.com
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post #1 of 12 Old 10-15-2019, 12:03 PM Thread Starter
mtsgsd
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I need a sanity check please

My brake suddenly went down almost to the floor yesterday. Brakes still there, but I had to pump them up and still had way too much travel. No leaks any where, fluid level is still correct. No excessive pressure required to operate the brake, so I figure the MC is leaking. The pedal hasn't been as firm as I would like anyway, even after replacing all calipers and bleeding out the system last year.

My problems started after I bled the new MC in place in the car (no bench or vise to mount it in) and found that the hydraulic lines wouldn't thread into it. I finally had to remove the whole thing, plus the two lines after disconnecting them at the abs pump (talking the two short lines to the MC). and thread them in that way. The threads were not cut well and it was impossible to start them by hand.

Ok, back on the car. I left the lines loose at the block and asked the wife to press the pedal so I could try and bleed some of the air out. She says "It doesn't move at all" then <snap> "oh it moves now".

Looks like I didn't get the MC lined up properly, but it found its place the hard way. Only thing is, the pedal travels all the way to the floor. no brakes at all now, and I can't seem to bleed it at the block. Surely I'd at least see brake fluid being pumped out? I also found that when the brake pedal is floored, and the engine is running, I now have a constant hiss.

Is it possible that the booster was damaged? I was about to just do a normal bleed since it has to be done anyway, but then I thought I'd see if anyone thinks I'm wasting my time. I do see the MC move when the wife applies the brake, so it seems we have a connection still. I'm doing this while sick so it's been real fun.


1999 WJ 4.7 Powertech
Quadra-Trac II 45RFE P245/70R16 GG AT2
Akebono front calipers
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post #2 of 12 Old 10-15-2019, 05:57 PM
2oldjeeps
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cant sort thru all that but in my experience,when the pedal goes to the floor the back brakes are bad even if front are perfect.back leaking or out of adjustment.
the rest idk...

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post #3 of 12 Old 10-15-2019, 05:59 PM
2oldjeeps
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cant sort thru all that but in my experience,when the pedal goes to the floor the back brakes are bad even if front are perfect.back leaking or out of adjustment.
the rest idk...
thats all cars ive owned,any kind

99wj,143,000 miles
00xj,177,000 miles
10hummer3,74,000 miles
98xj,130,000 miles
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post #4 of 12 Old 10-20-2019, 04:09 PM Thread Starter
mtsgsd
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Forget the sanity check the brain has already left the building. I misaligned the master cylinder and the rod from the brake booster broke of an edge of the MC and did enough damage that I had to replace it. I just got done doing that and bleeding the brakes (in the proper order) and damn if the pedal still doesn't go down to the floor. I have brakes, but only by flooring the pedal. The rubber lines in front were replaced last year, and there's no visible leaks anywhere. No visible change to the fluid level either. What the heck am I missing? I feel like a complete idiot right now.

1999 WJ 4.7 Powertech
Quadra-Trac II 45RFE P245/70R16 GG AT2
Akebono front calipers
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post #5 of 12 Old 10-20-2019, 06:29 PM
Mattyjm
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Originally Posted by mtsgsd View Post
Forget the sanity check the brain has already left the building. I misaligned the master cylinder and the rod from the brake booster broke of an edge of the MC and did enough damage that I had to replace it. I just got done doing that and bleeding the brakes (in the proper order) and damn if the pedal still doesn't go down to the floor. I have brakes, but only by flooring the pedal. The rubber lines in front were replaced last year, and there's no visible leaks anywhere. No visible change to the fluid level either. What the heck am I missing? I feel like a complete idiot right now.
You've still got air in the lines. Don't ever let the MC run dry. Since you swapped your MC, my guess is that you still have some air to get rid of.

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post #6 of 12 Old 10-20-2019, 07:40 PM Thread Starter
mtsgsd
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You'd think right? nothing from the wheels when I was done. Maybe still trapped in the MC? It came with a lame bleeder system that leaked air, but i did the best I could and figured the rest would be forced out during the bleed.

1999 WJ 4.7 Powertech
Quadra-Trac II 45RFE P245/70R16 GG AT2
Akebono front calipers
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post #7 of 12 Old 10-21-2019, 09:31 PM
the88thpianoman
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Quote:
Originally Posted by mtsgsd View Post
You'd think right? nothing from the wheels when I was done. Maybe still trapped in the MC? It came with a lame bleeder system that leaked air, but i did the best I could and figured the rest would be forced out during the bleed.
Still the most likely scenario is air in the lines, ABS pump, any little nook and cranny in the brake system.

Pressurized flush to rule out air bubbles and locate any unknown leaks is for sure the next step. I'd bring it to a shop for a pressure bleed, just be sure to ask if the shop if they do a computerized flush or just a gravity bleed. The ABS pump needs the computer hooked up to open the pump and flush the fluid/air.

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post #8 of 12 Old 10-22-2019, 06:06 AM
AVR2
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If there's air in the ABS pump, you won't know about it until the ABS is actually triggered. Air in the ABS has zero effect on normal braking.
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post #9 of 12 Old 10-22-2019, 04:29 PM Thread Starter
mtsgsd
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I finally got it. I've never had so much trouble bleeding brake lines. It's still not a hard pedal but it works. This was taking so long I was beginning to think there was something basic that I was missing. Thanks.
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1999 WJ 4.7 Powertech
Quadra-Trac II 45RFE P245/70R16 GG AT2
Akebono front calipers
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post #10 of 12 Old 10-22-2019, 11:10 PM
Mattyjm
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Originally Posted by mtsgsd View Post
I finally got it. I've never had so much trouble bleeding brake lines. It's still not a hard pedal but it works. This was taking so long I was beginning to think there was something basic that I was missing. Thanks.
The highest compliment that I never got from my dad was being a thorough mechanic. I try.

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post #11 of 12 Old 10-23-2019, 12:20 PM
2oldjeeps
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its a mystery why some are difficult. i did one cal up front and 2 in back. gravity bled ,then regular bleed. ez, brakes are fine. ???

99wj,143,000 miles
00xj,177,000 miles
10hummer3,74,000 miles
98xj,130,000 miles
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post #12 of 12 Old 10-28-2019, 03:10 PM Thread Starter
mtsgsd
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The brakes began to fade on me again. Strange behavior, they'd go almost to the floor and then suddenly be nearly normal. I finally found the culprit on Sat. The right rear brake line has a crack in it. It's exactly centered in one of the bending metal tabs that hold it against the axle. Even now the only reason I know about it is that the crack got big enough that I could see the oil leaking. I can feel the crack with my hand but I can't see it. JB Weld putty got it working for me again while I wait for the brake lines to arrive. The crack must have been so small originally that it was atomizing the fluid, because I never saw a sign of the leak. Heck, the brake fluid wasn't even going down originally. It did by last weekend though!

1999 WJ 4.7 Powertech
Quadra-Trac II 45RFE P245/70R16 GG AT2
Akebono front calipers
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