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Discussion Starter · #1 ·
I am replacing the frame on a 95 YJ after buying it in June and driving it all summer. Today I took a look at the brake lines, and was surprised to see that the steel brake line feeding the back brakes was rusted into pieces. The jeep passed inspection in June, and always stopped fine, although evidently only the front wheels were braking. It kind of seems impossible to me, to find the rusted line, gaping open, with no hint of leaking brake fluid. I can only assume the proportioning valve is messed up? Just wondered if anybody here has encountered something like this. Also wondering how it passed safety inspection - I guess the pads get checked but not the lines.
 

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I may be mistaken but on newer master cylinders, there are separate reservoirs for the front and back, os if the rear lines went out you would still have the front brakes..
 

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I may be mistaken but on newer master cylinders, there are separate reservoirs for the front and back, os if the rear lines went out you would still have the front brakes..
I believe that's correct but your brake light should have come on.
 

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I may be mistaken but on newer master cylinders, there are separate reservoirs for the front and back, os if the rear lines went out you would still have the front brakes..
Gary is partially right...
If that does happen the peddle would be super squishy! You'd be able to stop but not as quickly. You'd know there is an issue right off the bat if the above mentioned happened. Unfortunatley is just happend to me a couple of months ago. Went to stop and the peddle just went to the floor and slowly stopped me. Luckly these things pretty much stop the second you let off the gas so I didn't smear anything. To the OP...you positive it's a "live" brake line? Not just an old one that has been bypassed? Check your master cylinder, is there fluid in both reservoirs? Or just one? If there is fluid in just one then there probably an issue with the proportioning valve.
 

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Discussion Starter · #5 ·
Well thanks for the ideas all. I don't think I am dealing with seperate reservoirs as far as I can tell. There is only one cap, over one reservoir. And just to make sure I was not imagining anything, I looked again, and counted three lines coming out of the apportioning block - one for the front left, one for the front right, and one line that makes its way down the firewall until it ends in a rusty mess.
 

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That is a dual system, someone may have plugged the rear lines, look inside all the fittings to the rear.
 

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The hyd. manifold under ths MC has a 'shuttle valve' in it, so when you lose a brake line, the pressure of your foot on the brake pedal shifts this 'spool piston' and closes off the leaking side so you still have the other 'Half" of the brake system working...as was stated before you should also have a dash/brake service lite that is activated when this valve shifts...thats what the wires in the middle of the manifold are for..Remember when you get it fixed to re-center the 'spool' piston in the manifold or you will still have no rear brake because that 'port' is blocked off (sometimes you can re-center it by taking off the center [wired fitting] and loosening a 'bleeder' screw on the other 'system side' and sharply press the pedal to force the spool center again, otherwise you pull the wired fitting off and get a small pick or something and lever the shuttle spool back to center....there will be a 'groove' on the piston that should be centered in the hole so the wired switch will not be pressed when you re-install it on the 'hyd. valve body/ manifold'
 

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Discussion Starter · #8 ·
The hyd. manifold under ths MC has a 'shuttle valve' in it, so when you lose a brake line, the pressure of your foot on the brake pedal shifts this 'spool piston' and closes off the leaking side so you still have the other 'Half" of the brake system working...as was stated before you should also have a dash/brake service lite that is activated when this valve shifts...thats what the wires in the middle of the manifold are for..Remember when you get it fixed to re-center the 'spool' piston in the manifold or you will still have no rear brake because that 'port' is blocked off (sometimes you can re-center it by taking off the center [wired fitting] and loosening a 'bleeder' screw on the other 'system side' and sharply press the pedal to force the spool center again, otherwise you pull the wired fitting off and get a small pick or something and lever the shuttle spool back to center....there will be a 'groove' on the piston that should be centered in the hole so the wired switch will not be pressed when you re-install it on the 'hyd. valve body/ manifold'
Thanks Jerrey and all, I will make sure to check the spool piston out when I start re-assembling this thing. I never had any indication on the dash that anything was wrong, but that's not surprising with this jeep. So I guess another task will be figuring out why the dash light never came on. I look forward to driving with four brakes... what a luxury!
 

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The hyd. manifold under ths MC has a 'shuttle valve' in it, so when you lose a brake line, the pressure of your foot on the brake pedal shifts this 'spool piston' and closes off the leaking side so you still have the other 'Half" of the brake system working...as was stated before you should also have a dash/brake service lite that is activated when this valve shifts...thats what the wires in the middle of the manifold are for..Remember when you get it fixed to re-center the 'spool' piston in the manifold or you will still have no rear brake because that 'port' is blocked off (sometimes you can re-center it by taking off the center [wired fitting] and loosening a 'bleeder' screw on the other 'system side' and sharply press the pedal to force the spool center again, otherwise you pull the wired fitting off and get a small pick or something and lever the shuttle spool back to center....there will be a 'groove' on the piston that should be centered in the hole so the wired switch will not be pressed when you re-install it on the 'hyd. valve body/ manifold'

That is very good info. Is that something they starting doing on 95's and later? My 94 lost a rear line and lost all but 5% of the braking ability. I also noticed in the picture that the MC is different than mine. Mine is metal whereas the one off the 95 is plastic!?
 
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