4 wheel disc, mine suck! - Off-Road Forums & Discussion Groups
Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

 
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post #1 of (permalink) Old 10-14-2003, 01:38 PM Thread Starter
 
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4 wheel disc, mine suck!

Just finished a 4 wheel disc conversion. Here is a list of everything in the braking system that has been replaced so far, but they still suck.
-New Rear disc conversion from SSBC
-almost all new brake lines
- new, not rebuilt, 80' corvette master cylinder for 4 wheel disc
-new front calipers, rotors, pads

So basicaly everyting is new. I have bled and bled these things and they still suck. I bench bled the new master cylinder, gravity bled all the brakes, bled the brakes after pumping pedal 3 times and holding ect. last time I bled them I started at the rear furthest from the MC and worked my way up. After I bled the rears I had a very firm pedal. As soon as I started bleeding the fronts the pedal got softer and softer. They are so bad that in low range they will hardly hold the jeep on a hill. I dont think there is still air in the lines because consecutive pumps of the brake pedal do not make it firmer. My next area to look at is the proportioning valve on the drivers side frame rail. I dont know much about it, but it seems like the only thing left to look at. Please help, I want to drive the jeep more before snow starts falling, but at this pace I doubt I will. any suggestions/ replys are greatly appreciated. [img]images/graemlins/smile.gif[/img]
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post #2 of (permalink) Old 10-14-2003, 01:55 PM
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Re: 4 wheel disc, mine suck!

My Brakes were the same. I tried everything, then I finaly tried the best.

I just did a Hydro-boost and I love it. The brakes stop the jeep. Can you believe it. I recomend it for all jeeps that have converted to 4 wheel disks.

I used the total setup from an 87 Chev Suburban. I bought a rebuilt pump and new hoses. It runs the brakes and the ram stearing well.
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post #3 of (permalink) Old 10-14-2003, 01:55 PM
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Re: 4 wheel disc, mine suck!

did the push rod for the MC come with the kit? Made for your Tub? Metal or Fiberglass? I swapped out mine one time only to find that I needed to shorten teh Push rod because it wouldn't relieve pressure back to the MC and lock the brakes up. then i had one too short and i had to pump the brakes to get any pressure.

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post #4 of (permalink) Old 10-14-2003, 02:55 PM
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Re: 4 wheel disc, mine suck!

search some of my posts from earlier this year.. i went through a LOT of trial and error to get mine right..
heres what seemed to help...
on the yj/tj , the master cylinder is sealed to the booster.. if there is no seal, the booster doesn't do poop.
also, I had to gut my proportioning valve.
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post #5 of (permalink) Old 10-14-2003, 04:40 PM Thread Starter
 
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Re: 4 wheel disc, mine suck!

How exactly do you "gut" the proportioning valve? I was reading on the coloradoK5 site that I also frequent about the same thing. The guy took some parts out of the prop. valve on his blazer, but I did not really understand what he did. I have an old valve I was playing around with, but could not figure what, if anything, I shuold take out. I do believe the rubber gasket/ seal between the booster and MC is good and even if it wasn't I dont believe the pedal would talvel so far. If I turn the jeep off the brakes are harder to push than when it was running, so I think the booster is still working. When I get back from work tonight I'll try the search under your name for anything else that may help.
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post #6 of (permalink) Old 10-14-2003, 04:54 PM
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Re: 4 wheel disc, mine suck!

I had to shorten the push rod from the booster to the peddle. I cut the orignal "funny shaped" (for the brake light switch) welded an extention with inside 3/8 threads. Cut the original off and threaded to match the peddle end. It gives me a little adjustment for the heigth of the peddle.

My master cylinder is from Master Power Brakes and seems to match up just right.

I use a proportioning valve from Summit. I can lock up all wheels at the same time on a sandy street. Have not tried it in a panic stop on regular pavement.
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post #7 of (permalink) Old 10-14-2003, 05:24 PM
 
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Re: 4 wheel disc, mine suck!

Not sure if this will help, but it is a very handy tool to have.

I picked up from Autozone a brake bleeder, vaccume pump tool. It came with a bunch of accessoires to help bleed your brakes by yourself. When i replaced my master cylinder, wheel cylinders and calpiers all at the same time this tool made it almost to easy to bleed the brakes. With all original brake parts i can lock up all the wheels at the same time now. Maybe drop the $25 it cost and try bleeding your brakes again. If noting else you will have a handy tool you will use again that doesn't cost to much.

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post #8 of (permalink) Old 10-14-2003, 10:26 PM
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Re: 4 wheel disc, mine suck!

Couldbe that the master cylinder bore is to small for the calipers you are useing... And all the disk swaps i have seen they dont use a prop valve..
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