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Old June 29th, 2013, 12:44 PM   #1
BigBird
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Default Having troubles with my disc brake conversion on my yj...

I had stock 30/35 axles under it with drums on the rear... Brakes worked good.
Changed axles to
Dana 44 scout in front with GMC 1/2 ton calipers
Dana 44 scout rear with GMC car front calipers (at least that's the pads that fit, just put new ones on)
94 yj booster and master cylinder with proportioning valve and all new flex lines front and back.

Problem is that I cannot bleed the brakes enough to get a good feel on the pedal. Bleed the brakes, no air coming out any of the calipers, and still the pedal is almost on the floor. It'll barely hold it on a hill... The brake light is on in the dash. No amount of pumping the pedal will get it to go out.

Any ideas??

Thanks for the help.
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Old June 29th, 2013, 01:13 PM   #2
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My pedal has never felt as good since I went disc brakes.
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Old June 29th, 2013, 01:14 PM   #3
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first the yj prop valve is set of for rear drum brakes, unless you drilled it out?
try a vacuum bleeder, it will get trapped air better, if there is any.
the highest point in the rear hardlines on a yj can hold air sometimes, it gets trapped.
is the booster and master combo new, reman, or used?
pedal rod the correct length? vacuum leak going to booster mabey?

just a few thoughts.
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Old June 29th, 2013, 01:14 PM   #4
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Quote:
Originally Posted by BigBird View Post
I had stock 30/35 axles under it with drums on the rear... Brakes worked good.
Changed axles to
Dana 44 scout in front with GMC 1/2 ton calipers
Dana 44 scout rear with GMC car front calipers (at least that's the pads that fit, just put new ones on)
94 yj booster and master cylinder with proportioning valve and all new flex lines front and back.

Problem is that I cannot bleed the brakes enough to get a good feel on the pedal. Bleed the brakes, no air coming out any of the calipers, and still the pedal is almost on the floor. It'll barely hold it on a hill... The brake light is on in the dash. No amount of pumping the pedal will get it to go out.

Any ideas??

Thanks for the help.
Try cracking one line at a time at the master while under pressure, if the brake light is on the master is dry.

I went through the same thing when I replaced all of the nasty original lines on my Yj. I spent an hour going from wheel yo wheel trying to get some pedal and could not. I cracked the rear line at the master w/ the pedal pumped up and a big burst of air came out. Started back at the furthest tire working my way around and had great pedal in 15 min.

Good luck!

Edit, with 1/2 ton calipers all the way around you brake pedal is not going to be the same. A 3/4 ton master and booster will make for great pedal feel. Gut your prop valve or buy an open one, no need to divert pressure w/ 4wheel discs!

Last edited by yyj87; June 29th, 2013 at 01:18 PM.
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Old June 29th, 2013, 08:43 PM   #5
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Awesome help... I will report back after it try a few things... It is a stock master and booster for the 94. I thought it was one of the ones guys swapped into their heeps. Thanks again.
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