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Brakes Binding after MC and line change

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    Brakes Binding after MC and line change

    I've had some terrible karma for my CB this year. The BMC seal started leaking a few wks ago and finally got bad enough to change last weekend. I got a new one, primed it, and changed it. Easy cheese. Changed out the crusty old brake lines w/ some Techna-fit SS ones while we were bleeding the system. Equally easy cheese.
    BUT! after driving a few minutes and warming up, the brakes start tightening up and the pedal gets super stiff. After a minute, it binds up and won't get out of 2nd cause it's pushing against the brakes. It's OK when it cools down. Fluid is new DOT4 and at good levels. I do have ABS (didnt work since we got the car) but dont know a thing about working on it.

    This happen to anyone else or just have ideas? I wanna be running stable when the Bisi header gets in!

    #2
    sounds like a bad compensating valve in the master cylinder to me.

    the compensating valve allows the fluid pressure to go back into the resavor when the fluid is heated up (expansion). however when it is clogged or bad then the pressure resides on the calipers tightening on the calipers and locking them up.
    What makes me laugh about forums, is that no matter how much you try to help someone, they dont take the advice. Go ahead and do it the hard way.

    You got to respect what you drive, and appreciate what you have, making the best of what you got. and if that means putting CAI, HID's, a phat stereo system, and a idiot in the drivers seat...then so be it!

    Retro!

    Hater

    I love nooBs...They make me look good

    Comment


      #3
      +2 for the comesation valve someone had the same complaint at work and thats what it was

      Comment


        #4
        when you guys say compensation valve do you mean the prop valve that people change to the 40/40 one from the integra when doing a rear disc swap?

        Comment


          #5
          so this compensation valve lets fluid back into the reservoir. That fits the description pretty well
          -if that's the problem, does that mean my brand new BMC is broken? Is that something fixable?

          -just curious, on the BMC, there's a hex hole b/n the brake lines and another on the opposite side. What are those for exactly?

          Comment


            #6
            sometimes the port can be clogged, and its in the BMC.

            But get another one, usually they have a warrenty of a few years.
            What makes me laugh about forums, is that no matter how much you try to help someone, they dont take the advice. Go ahead and do it the hard way.

            You got to respect what you drive, and appreciate what you have, making the best of what you got. and if that means putting CAI, HID's, a phat stereo system, and a idiot in the drivers seat...then so be it!

            Retro!

            Hater

            I love nooBs...They make me look good

            Comment


              #7
              sadness! I got the Cardone "Select" one from RockAuto (fantastic price). I can't go home for 2wks to swap it. Better to do it again or get a brake shop to do it?
              also, I bled the lines since I went SS at the same time, but do you have to bleed the wheels just doing MC change?

              Comment


                #8
                Originally posted by Shankenstein View Post
                sadness! I got the Cardone "Select" one from RockAuto (fantastic price). I can't go home for 2wks to swap it. Better to do it again or get a brake shop to do it?
                also, I bled the lines since I went SS at the same time, but do you have to bleed the wheels just doing MC change?
                if you did it urself before then id do it myself again.

                Yes you have to bleed the system again.

                if anything contact rockauto, and tell them its bad. ask for a retrun. Then go to the store and just buy another one.
                What makes me laugh about forums, is that no matter how much you try to help someone, they dont take the advice. Go ahead and do it the hard way.

                You got to respect what you drive, and appreciate what you have, making the best of what you got. and if that means putting CAI, HID's, a phat stereo system, and a idiot in the drivers seat...then so be it!

                Retro!

                Hater

                I love nooBs...They make me look good

                Comment


                  #9
                  To my knowledge, CB7 master cylinders have a (rather primative) proportioning valve between the 2 outlets. You can see the black dot, with a gray "O" around it, in this picture.



                  The idea is that you press the pedal, and pressurize fluid in the cylinder. The full pressure goes to the front brakes. The proportioning valve creates a pressure drop, and your rear brakes receive the (total pressure - pressure drop).

                  As I mentioned, it's primative, compared to Combination valves, How Combination Valves Work! but it does give the ability to adjust the front/rear brake bias. Similarly, the ABS solenoid valves control each wheel individually.

                  Ex:
                  When the valve is fully open, brake pressure is 50%-50%... fully closed is 100%-0%. Personally, I don't know what the proper distribution is, but I image it's similar to the weight distribution (about 60%-40%)


                  Questions for the CB Gurus:

                  1) What is the proper position for the proportioning valve?

                  2) Do Cardone Select (and other manufacturers) set the valve properly before it leaves the factory?

                  3) Couldn't a failing/sticky brake booster cause this problem too?

                  Comment


                    #10
                    @Tinman, there are the 2 chambers but isnt there a return channel in each piston? There's a chance the piston cup (after the push-rod, before the front chamber is blocking the fluid return hole.

                    Comment

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