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Old 11-26-2010, 05:29 PM   #1
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brake question for 8.8 guys

hey, i just finished swapping the 8.8 into my tj and did new hardlines, new calipers and new pads. also put in an '03 rubicon proportioning valve. after bleeding the brakes3 times, the brakes still suck! it slows down like a mack truck, super spongie and cant possibly lock them up. does anyone have any ideas as to how i can fix this? its now my DD as of today and i NEED to fix this any ideas would be great, thanks

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Old 11-27-2010, 07:09 AM   #2
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Really need help here.

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Old 11-27-2010, 08:26 AM   #3
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You changed the hard lines, keep on bleeding till you can't bleed no more! Seriously though, use a rubber clear tube on the bleeder valve and keep an eye for ANY bubbles while you bleed. I replaces one of my front hard lines and I had to bleed it like 15 times. It still feels like there's a little air in there
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Old 11-27-2010, 08:29 AM   #4
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Quote:
Originally Posted by MikalCarbine View Post
You changed the hard lines, keep on bleeding till you can't bleed no more! Seriously though, use a rubber clear tube on the bleeder valve and keep an eye for ANY bubbles while you bleed. I replaces one of my front hard lines and I had to bleed it like 15 times. It still feels like there's a little air in there
Ya we used the clear hose and saw a little air the third bleed but it seemed to only get worse. Strange,
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Old 11-27-2010, 08:32 AM   #5
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Keep on trying, you may never get it perfect and need to rebleed every week or so for a while. You bled in the proper order I am assuming right?
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Old 11-27-2010, 08:56 AM   #6
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Bled the rear brakes first then the front. What should I have done?
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Old 11-27-2010, 10:03 AM   #7
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If my memory serves me correct you want to start farthest away from the master cylinder and then work your way closer. This would be rear passenger, rear driver, front passenger and finally front driver.

Did you introduce air into the master cylinder at all during the process of installing the rear or did you just play with the proportioning valve
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Old 11-27-2010, 11:34 AM   #8
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make sure ur not getting air into the sys via a loose connection but it does take a while to get all the air out. Also try lightly tapping on the lines and caliper w a screwdriver handle to dislodge any small air bubbles
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Old 11-27-2010, 12:17 PM   #9
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We Just messed with the proportioning valve. It's defiantly an air feeling but I figured it could be under powered because I read about using a hydro boost system on stu olsens site to stiffen the brakes up.
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Old 11-27-2010, 01:49 PM   #10
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Do you get the air feeling while pumping the brakes while not moving? The air feeling should be a spongy feeling in the pedal where you can push the pedal down a few more inches than it normally would top out at
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Old 11-27-2010, 03:23 PM   #11
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Do you get the air feeling while pumping the brakes while not moving? The air feeling should be a spongy feeling in the pedal where you can push the pedal down a few more inches than it normally would top out at
moving or driving they feel the same, its just what your describing, the pedal goes down inchs further than its supposed to and the braking power just isnt there.

what is the rubber piece on the back of the proportioning valve? although the valve is brand new could that have anything to do with this?
i can bleed it again and try that but i feel like theres another issue causing this problem
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Old 11-27-2010, 05:27 PM   #12
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Many have been through this as I have . The proportioning valve was no different than the one you removed believe it or not new part # same valve. I complained about the soft feeling pedal after spending hours bleeding with out a drop of air in the fluid. In the end I installed two new rotors and EBC Green pads only because no one had yellow. I am happy with the brakes now even though the pedal is not really much better. The rear brakes on a TJ don't do a lot of braking by design . If the proportioning valve divided the pressure 50/50 we would not stop as quick as half of the pressure would locking up the rear brakes right away ( not much weight on the rear when brakes are applied ) and the front brakes which would now have most of the vehicles weight on it would only have 50 percent of the preasure . To my understanding when you nail the oe brakes initially the rear get a a high amount of preasure for a fraction of a second which is to give the same effect as an anchor would on the back of a boat it pulls the vehicle straight then the spring and the valve part of the proportioning valve lower the rear preasure and apply more to the front wheels where most of the weight is now transfered to and we stop. That is why you see brake upgrades for the front as that is where most of the stopping is done . I will provide a few links to where myself and others have been through this as well as the master cylinder swaps that will give you a harder pedal making you think you have fixed it but have not . You will find if you have good pads , rotors ,no leaks and no air you will be about the same as you were before the 8.8 swap if your drum brakes were working as well as most are which is marginal . All you have gained by discs on the rear is brakes less efected by water and less maintainace and less braking surface. I know it don't sound right as it didn't to me but one man in particular who goes by the username of Mr. Blaine on a few forums is as smart as they get on brakes and has the experience to back up what he says. do a lot of searchs and you will probably be like I was , thinking I had more of a problem than I did.
http://www.jeepforum.com/forum/f9/fo...-valve-811930/
http://www.jeepforum.com/forum/f9/pr...8-swap-977647/
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Old 11-27-2010, 06:03 PM   #13
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the proportioning valve info is just what I have read and not experienced yet so it is not something etched in stone . I am still searching for more of the posts that helped me get rear barkes finished on my 8.8 swap.
http://www.pirate4x4.com/forum/showt...ft+brake+pedal
http://www.jeepsunlimited.com/forums...d.php?t=371713
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Old 11-27-2010, 06:39 PM   #14
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30 minute limit on editing isn't helping . I have to make a new post again . Any way this should be enough info to get you through it . 4 wheel disc brakes - JeepsUnlimited.com Forums
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Old 11-27-2010, 09:31 PM   #15
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gary2, thanks alot, thats exactly what i needed to point me in the right direction. i wish i knew this earlier, i wouldnt have bought the brake and rotor kit, ha. do you think we would benifit from doing the hydro boost setup on stu olsens site? im planning on doing some light towing and have to improve them significantly.

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