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  • Can anyone shed some light on a CJ-5 Brake issue

    I am trying to resolve an issue on a 1980 CJ-5 with brakes and air in lines.

    This is my father's Jeep and he has gone through what I consider overkill steps to resolve this problem. First the problem and then what he had done to resolve to no avail. The jeep after a brake job somehow is still getting air in the lines on the front only. The rear brakes are great which are drums but the front which are disc even after pumping up and bleeding still are getting air back in the lines and causing the pedal to not hold. When you jack the jeep up and pedal is depressed you can turn front wheels but can't turn rear ones. Upon rebleeding the front there will be more air each time.

    Now for the steps he has taken. First there are no visible leaks. The master cylinder was first suspect. It was replaced with a rebuilt piece. When it didn't cure the problem it was first assumed to be defective. It was replaced a second time. Same problem so this time it was replaced with a NEW unit. Same problem. After that the proportioning valve was replaced with a NEW OLD ORIGINAL piece from a Jeep specialty company. Both calipers, both wheel cylinders and still the same issue.

    The rear brakes will hold and even lock if jammed to the floor but the front are non-existent.

    I have been told to bench bleed the master cylinder. Sorry guys I am somewhat a gearhead and even a co-owner in a new technology of spark plugs but don't know the procedure to bench bleed.

    Is it possible that air could be getting back in the lines while bleeding utilizing two people before the brake bleeder screws are tightened?

    Are the speed bleeders designed to keep air out and bleed with one person worth trying?

    I have reached the point of trying anything that anyone might suggest. Even replacing every single line.

    HELP!

    Rick H

  • #2
    Bench bleeding is a pretty simple thing to do and should be done when the m/c is changed. There is a kit, some masters come with it some do not, that has fittings and some lengths of tubing that you will run from the fitting hole on the master and the tubing will run back into the resivor(sp). Then cycle the master. It can be done on or off the vehicle. This will force the air in the chamber out. I would give this a try before you change the hoses.

    Comment


    • #3
      Rick, to bench bleed the master cylinder it is pretty easy to do. Take the MC and place it on your work bench. There should have been a bench bleeding kit that came with it, there should be 2 fittings(plastic) and 2 small hoses(also plastic) in a bag. Take the fittings, put them in the MC where the brake lines come out and put the hoses on those and feed them back into the MC reservoir. You will do this with the lid off of the MC. Pump it up with a screwdriver until there are no bubbles coming out of the tubes into the MC. All this does is ensure that there is no air in the MC before you put it on the Jeep. It helps minimize the bleeding time. After you have all the air out, just keep the tubes and fittings in the MC till you place it in the Jeep, then pull them out just before you put the lines in.

      Now that is kinda FYI at this point.

      You say that the front brakes keep getting air in them, that tells me that there may be something going on at the proportioning valve. I see that it is a new unit, but I would double check it. From the info you first sent me, I mis-understood, I thought you were getting air all the way around. But I see that it is just the front, that tells me the proportioning valve is questionable.

      Scrambler

      Comment


      • #4
        Did you hold the pin on the proportioning valve in when you bleed the brakes? The pin on the front of the valve needs to be held in when bleeding the system to allow air to pass through the valve. I just used a 'C' clamp to hold the pin in.

        Speed bleeders are worth the money. They make bleeding the brakes much easier and it can then be done with only one person. You can buy them for around $10 a pair at AutoZone or Pepboys.


        Is one of the resivoirs in the master cylinder draining. If it is draining then you have a leak somewhere. If you are not loosing fluid then you just have air trapped in the system. When I switched to a YJ booster and MC on my CJ I had to bleed the system 3 or 4 times before I got all of the air out of it.

        Good Luck.

        Comment


        • #5
          Bench bleeding:
          http://www.superchevy.com/technical/...nch/index.html

          I know it's a Chevy article but it works as a link.

          Comment


          • #6
            There is a special tool to hold the metering valve while bleeding the brakes on CJ's with front disc brakes (Tool J-26869). I guess you might be able to improvise with something else, but I'd guess that this is the cause of your problem.

            Comment


            • #7
              Originally posted by scrambler013
              Rick, to bench bleed the master cylinder it is pretty easy to do. Take the MC and place it on your work bench. There should have been a bench bleeding kit that came with it, there should be 2 fittings(plastic) and 2 small hoses(also plastic) in a bag. Take the fittings, put them in the MC where the brake lines come out and put the hoses on those and feed them back into the MC reservoir. You will do this with the lid off of the MC. Pump it up with a screwdriver until there are no bubbles coming out of the tubes into the MC. All this does is ensure that there is no air in the MC before you put it on the Jeep. It helps minimize the bleeding time. After you have all the air out, just keep the tubes and fittings in the MC till you place it in the Jeep, then pull them out just before you put the lines in.

              Now that is kinda FYI at this point.

              You say that the front brakes keep getting air in them, that tells me that there may be something going on at the proportioning valve. I see that it is a new unit, but I would double check it. From the info you first sent me, I mis-understood, I thought you were getting air all the way around. But I see that it is just the front, that tells me the proportioning valve is questionable.

              Scrambler

              I always bolt the m/c into the jeep when i bench bleed. Then just put some old lines on and bend them into the res. Get in jeep, press and release pedal a bunch of times, and presto, bench bled. same principle, but you dont have to mess around with a vise.
              Also, are you sure the calipers are on the right sides. The bleeder screw needs to be on the top of the caliper, otherwise air will stay stuck in there. Some parts houses list the part numbers in reverse, depending if the caliper is mounted towards the front or rear of the vehicle.
              Another thing, my jeep has great brakes, and i never messed with the pin on the prop. valve.

              nutt....
              ps. speed bleeders are worth their weight in gold, especially if your wife can't figure out how to 'pump and hold, release'

              Comment


              • #8
                this sounds like a definite maybe...

                Originally posted by nuttzach
                ...Also, are you sure the calipers are on the right sides. The bleeder screw needs to be on the top of the caliper, otherwise air will stay stuck in there...
                This is a good one, Nutt. I've been thinking about this thread since I read it earlier. 'Somewhere' on here, months and months back, someone posted after trying everything that they had the calipers upside down.

                It could be that there was a bad 'new' master cylinder then the calipers were installed wrong while doing the 'let's replace everything' deal.

                Comment


                • #9
                  S.w.a.g.

                  I've never messed with a proportioning valve, so this may be for nothing.
                  Could the valve or lines be reversed? If it takes more pressure on disc than drum, it sounds reasonable. Just guessing

                  Comment


                  • #10
                    One thing on CJ's as well,you need to bleed the fronts,then bleed the backs,and go back and do the fronts.This will "center" the prop valve pin and allow proper bleeding.
                    There's a write up in my '79 service manual,I just don't have it here.
                    I can check it out tonight and post tomorrow if you want the actual article.

                    Ragg
                    Last edited by raggmann; 10-11-2007, 10:05 AM.

                    Comment


                    • #11
                      I was going to suggest the calipers on upside down. I can't remember if I was the one that said it awhile back as blackwater said but I did indeed run into the problem after converting mine from front drum to front disc. Not having experience with the discs I just never thought about it. Drove myself crazy until I got a mechanic buddy to come over and look and he saw it in about 10 seconds.

                      I also just put a master cylinder on mine about 2 weeks ago and "bench bled" mine attached to the Jeep utilizing the enclosed fittings and tubing. As someone else said I just pumped the pedal. I can tell you that you also need to make sure to take a small hammer and tap the bottom of the master cylinder as that will get additional air out. It appeared at one point that I had bled all the air out by using the pedal but it took about another half hour or more of tapping to get every last bit of air out.

                      Comment


                      • #12
                        It might be a trapped air pocket somewhere. Try starting with a gravity bleed and finish up with the standard "pump and bleed" method.

                        It's best to start with the bleeder furthest the MC. Top off the MC and open the RF bleeder at the caliper. Leave it open until you see no more air/bubbles pushing out of it. This could take 5 minutes or more. Keep and eye on the brake fluid level in the MC. You can leave the top off the MC so you can watch it and add accordingly.

                        Once that side is done, close the bleeder and do the same to the drivers side, while watching the fluid level.

                        At this point you should have the majority of the air out and be able to bleed whats left in the lines by the standard pump method. Ensure the bleeder is closed BEFORE your assistant releases the brake pedal each time.

                        Hope this helps.
                        Last edited by xlr8n; 10-11-2007, 01:44 PM.

                        Comment


                        • #13
                          If you have done all of the above and still have the same problem try taking the calipers off the rotors and cracking the bleeders and pushing the piston back in. It is not a real common thing but air can get trapped past the bleeders and the piston and the only way to get it out with basic tools is to push it back out with the bleeders open. If you see any air or spitting that would be your problem. After getting the piston back in then try bleeding
                          as before.

                          Comment


                          • #14
                            Had a problem with my ram front brakes after replacing bearing hubs. Had put an extra twist in the calipers causing the brake hoses to kink. Was a ***** to stop till I figured the hoses were pinched off. Just a thought.

                            Comment


                            • #15
                              Originally posted by cj5kb
                              I was going to suggest the calipers on upside down. I can't remember if I was the one that said it awhile back as blackwater said but I did indeed run into the problem after converting mine from front drum to front disc. Not having experience with the discs I just never thought about it. Drove myself crazy until I got a mechanic buddy to come over and look and he saw it in about 10 seconds.

                              I also just put a master cylinder on mine about 2 weeks ago and "bench bled" mine attached to the Jeep utilizing the enclosed fittings and tubing. As someone else said I just pumped the pedal. I can tell you that you also need to make sure to take a small hammer and tap the bottom of the master cylinder as that will get additional air out. It appeared at one point that I had bled all the air out by using the pedal but it took about another half hour or more of tapping to get every last bit of air out.
                              Thanks for the advice. We bench bled the master cylinder and put the aftermarket speed bleeder screws on and then tried bleeding the system again using a c clamp to hold in the button on the proportioning valve. They are better but still getting air or have it trapped somewhere. This is about the most aggravating brake problem I have ever encountered. I will try tapping on the master cylinder next. Thanks.

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