[GirlfriendYJ]

i am still having some brake issues...

this is on a 91 yj using 1/2 ton chevy calipers in the rear and the dual piston calipers in the front...i also have the 78 mercury marquis with 4 wheel discs and hydroboost master cylinder...

this setup works great but after a little use the brakes begin to lock up and then i have to open each bleeder and release the pressure...

i have heard several theories on this, and will gladly listen to others....

here are my plans...get a new MC..s.ame one under warranty....bench bleed and install

then i am going to take out the little block that comes stock on jeeps and just use a T for the front brakes...

then i am going to put an adjustable valve for the rear....

http://store.summitracing.com/defau...word&searchtype=both&part=proportioning+valve

which one is recommended....any reason to go with the $70 over the standard $40?

then with a good power bleed i should be okay...

thanks, kosta

 

[Surfzup2k3]

I ran across a thread the other day about this EXACT same thing. Search in the Jeep section for something like master cylinder upgrades or something like that. Had a solution in it too, even though it wasn't what i was looking for, i read it anyways.

 

[usmcdoc14]

what proportioning valve are you using now?
what brakes are locking up? (front/rear/both)


and then i will give ya my idea of what is wrong/how to fix :flipoff2:

 

[GirlfriendYJ]

what proportioning valve are you using now?
what brakes are locking up? (front/rear/both)


and then i will give ya my idea of what is wrong/how to fix :flipoff2:

no proportioning valve...just the block under the MC right now....there was an oring in it that i took out for the rear, and it helped some....

all of them lock up

whats the advise?

thanks:flipoff2:

 

[GirlfriendYJ]

I ran across a thread the other day about this EXACT same thing. Search in the Jeep section for something like master cylinder upgrades or something like that. Had a solution in it too, even though it wasn't what i was looking for, i read it anyways.

http://www.pirate4x4.com/forum/showthread.php?s=&threadid=197993&highlight=master+cylinder

that post? looks like his was solved by getting a different MC....

 

[jeepnmatt]

it sounds like the piston in the MC is not being allowed to return all the way back to its "neutral" position and is holding pressure.

it could be that the push-rod between the MC and booster is too long, or it could be that the booster push-rod to the pedal is too long.

first, i'd unhook the one from the pedal and see what it does at rest. it could be forcing the pedal back against the stop on the pedal assembly. if it is, then it should be shortened...i'd make it adjustable by threading the rod and putting a heim joint on the end (if it will work with the pedal). if everything seems cool there, look at the push-rod between the MC and booster. the local autoparts should have adjustable ones of these or make some temporary pushrods and test them out.

 

[PIA]

sounds like you may have rod issues....

but I'm using a similar setup.....hydroboost, fullsize chevy front brakes (80s truck), rear monte carlo discs, with a 82 corvette master cylinder, and a 95 Jeep ZJ prop valve (which is front/rear disc setup).


works great!

 

[usmcdoc14]

rod to long or MC is shot, follow the above advice

 

[Surfzup2k3]

http://www.pirate4x4.com/forum/showthread.php?s=&threadid=197993&highlight=master+cylinder

that post? looks like his was solved by getting a different MC....

thats the one i was talking about.... sorry it couldn't help

 

[GirlfriendYJ]

thanks guys...

since the MC i have is under warranty, i am just gonna pull it and get a new one and start from scratch with it...

as far as the push rod....mine is already adjustable....its on a YJ...

how do i know how long it should be? should it be touching the piston without any pressure on the pedal? or should it be some distance away?