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  • Proportioning valve help...79 cj5

    Can anyone tell me if a bad or not properly working proportioning valve can cause this problem im having. Ive changed everything on all 4 wheels as far as brake parts...even 2 master cylinders. But still the brake pedal will pump up hard on 2 or 3 pumps and hold till i take my foot off. Then i can immediately push the pedal again and it will go to the floor as easily as the clutch. And sometimes it wont even pump up. I know it seems like there has to be air in the lines but i have bled a gallon of break fluid thru it and can get no air to come out. It has manual brakes..... Please help.

  • #2
    easy as the clutch...

    ...which means you still have 'some' resistance? Do you have disc up front, drum rear? If your proportioning valve is not holding residual pressure on the rear drums it 'could' be causing this. However, losing such a large amount of pedal so quickly sounds like you might be bumming out on 'new' master cylinders. Are you bench bleeding the masters? Also, do a search and make sure you're bleeding the wheels in the proper order. I forget it at the moment. Maybe some of the guys will chime in with that. OR... you can search again. Oh, and welcome to the board, dwb!

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    • #3
      Yes there is a tiny bit of resistance but not much when it is not pumping up hard, i have disc on the front and drums on the back. I did bench bleed the master cylinders and and as far as the brake line bleeding i start at the passenger back wheel then driver side back wheel then passenger front and driver front last.
      The master cylinders have both been re-manufactured so i was kinda thinking too about trying one from a different autoparts. Ive heard about gravity bleeding but not sure on how to do that... like do i open all the bleeders at one time for that and just keep filling the master cylinder? And how long do i leave them open...an hour or so or longer? Thanks again for your help Blackwater.
      Last edited by dwb1500; 04-07-2006, 08:35 AM.

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      • #4
        When bleeding brake lines, US models, start with RR cylinder, then LR, then RF and finsh off with LF.

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        • #5
          expensive parts...

          The proportioning valve is expensive for the CJ, DWB. However, I've read that the YJ valve will work and it's cheaper. (I don't know why.) Before you replace the valve you might want to rig some sort of tubing deadhead so that you're exercising just the master without pressure going to the brakes. (This would require gathering some fittings and a small amount of tubing.) You could then test the cylinder by itself to see if its working properly. I've had some pretty bad luck with rebuilt, even new parts from the big chain parts stores. Maybe you should consider a new master from 4WD once you determine where the problem is. (They sell the prop valves, too.)

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          • #6
            Thanks for the input guys. I will try to isolate the master cylinder to see if its the problem. Im glad i found this forum.....ya'll have already given me way more input on the matter than anybody at these parts houses ive been dealing with !!
            Thanks again

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            • #7
              i dont' see it being the portioning valve. sounds like contaminants in the line(s) or bad M/C.

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              • #8
                Originally posted by FUBAR
                i dont' see it being the portioning valve. sounds like contaminants in the line(s) or bad M/C.
                Yeah. Short of a leak that you would of noticed, even if everything failedinside it should still pump up and maintain pressure.
                http://www.dana60.com/76cj5/provalve.jpg

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                • #9
                  Dang!

                  Originally posted by John Strenk
                  Yeah. Short of a leak that you would of noticed, even if everything failedinside it should still pump up and maintain pressure.
                  http://www.dana60.com/76cj5/provalve.jpg
                  You got cool pics, John...

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                  • #10
                    Usually the easiest solution is the problem, my guess would be air in the lines. I had trouble on my XJ at one point when I replaced both rear cylinders. We could not get it to have full pressure when the engine would turn on (power brakes). We had it towed to a local brake company and they went through 6 qrts of brake fluid till they got the air out of the system.

                    Good luck, I will be checking in to see what actually happens!

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                    • #11
                      Originally posted by rstarch345
                      When bleeding brake lines, US models, start with RR cylinder, then LR, then RF and finsh off with LF.
                      That's where I read that!!!
                      I just replied on his post regarding his brakes .... I think it may be the rear shoes not set up properly.
                      Both CJ axles I have worked on have had a longer line to the LR than to the RR (same distance to the tee) so it would be furthest from the master cylinder. Works for me anyway.
                      Most repair shops can use a vacuum/pressure system to make sure your lines are air free if you're still unsure.

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                      • #12
                        Originally posted by blackwater
                        You got cool pics, John...
                        damn cool pics....that topic has floated around here forever, and you just answered all questions with one pic.

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                        • #13
                          things that make you say Hmmmmmmm.....

                          I doubt it is the proportioning valve... the entire system is a sealed system which means if you are losing pedal pressure that brake fluid is going somewhere else or you have air in the system. be sure to check the condition of the brake lines (nothing ballooning??!). Also, if you do decide to change out the valve, be sure you get the one for disc fronts... otherwise the lines won't fit properly and if you modified them to fit, your brakes will not work properly.

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                          • #14
                            great diagram

                            Originally posted by John Strenk
                            Yeah. Short of a leak that you would of noticed, even if everything failedinside it should still pump up and maintain pressure.
                            http://www.dana60.com/76cj5/provalve.jpg
                            This is a great drawing; I added it to my library!! I ma wondering what other great jeep parts drawings are floating around out there in e-land... maybe we should add another message folder to the forum here for nothing but great diagrams like this one - I know I would use it!!

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                            • #15
                              Righto.....sounds like John ought to start it?

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