Disc Brake conversion - can’t get pedal pressure

Brakes, Steering & Suspension

  1. 65_Satellite

    65_Satellite Well-Known Member

    Messages:
    85
    Likes Received:
    111
    Joined:
    Jan 10, 2021
    Location:
    01543
    Local Time:
    4:11 AM
    I read through some of the other forums and didn’t see anything that helped. I recently converted my 65 Satellite to manual front discs. I used the Right Stuff Detailing disc brake kit which came with the 15/16 master cylinder, adjustable pushrod, adjustable proportioning valve, spindles, rotors, calipers and hoses. I also purchased from Inline Tube the complete hardline brake lines from front to back. I then bought the complete rear drum rebuild kit from Doctor Diff with new wheel cylinders. So I ultimately have an entirely brand new brake system in the car. I do want to note that I re-used the brake pedal pushrod from my single reservoir master cylinder as that has the bump in it that activates the brake light switch under the dash. The adjustable pushrod was not the same design and would not come close to the brake light switch to activate it. My issue is I’ve bench bled the master, and installed it and bleed the brakes all the way around going from right rear to left rear to right front to left front. After an hour or so, there appears to be no more air bubbles but the pedal is very spongy and goes right to the floor. If I have someone pressing the pedal, I can see the rear drums activating as they should and if it spin the drums and have someone hit the brakes, it stops them. The front discs are really tight fit and it’s hard to move the rotor but I can (with a lot of drag) and if you hit the pedal it stops them from moving. So they seem to be operating but the pedal is so soft and travels all the way to floor. What am I missing here? What can I do to get more pressure and prevent the pedal from going to floor?
     
    Last edited: May 1, 2021
  2. Beekeeper

    Beekeeper It’s a disease without a cure! FBBO Gold Member

    Messages:
    4,056
    Likes Received:
    4025
    Joined:
    Jul 4, 2012
    Location:
    Rogersville,TN.
    Local Time:
    3:11 AM
    Did you install a residual valve in the master rear brake port or in the line?
    You gotta have this valve to hold residual pressure in the rear wheel cylinders
    The springs on the rear shoes will retract them too far from the drums and will cause them to travel too far before contacting the drums. This will cause the problem you are having. Also are these power brakes?
     
    • Like Like x 1
    • 65_Satellite

      65_Satellite Well-Known Member

      Messages:
      85
      Likes Received:
      111
      Joined:
      Jan 10, 2021
      Location:
      01543
      Local Time:
      4:11 AM
      These are manual disc/drum. I don’t know what a residual valve is. Are you referring to the proportioning valve?
       
    • hunt2elk

      hunt2elk FBBO Gold Member FBBO Gold Member

      Messages:
      8,727
      Likes Received:
      8222
      Joined:
      Jul 15, 2009
      Location:
      WI
      Local Time:
      3:11 AM
      From what I have learned, all the newer rear wheel cylinders do not need a residual valve in the master cylinder. None of the aluminum masters that Dr Diff sells have the valve. The cast iron versions that I don't believe he sells anymore did come with the valve installed in the rear line port.
      To me it sounds like there is still air in the system, or a bad master cylinder.
       
      • Agree Agree x 2
      • Like Like x 1
      • 65_Satellite

        65_Satellite Well-Known Member

        Messages:
        85
        Likes Received:
        111
        Joined:
        Jan 10, 2021
        Location:
        01543
        Local Time:
        4:11 AM
        This is the second master cylinder. The first one had an issue with the threads in the front port and it kept leaking. They sent me a replacement one that I just installed.
         
      • hunt2elk

        hunt2elk FBBO Gold Member FBBO Gold Member

        Messages:
        8,727
        Likes Received:
        8222
        Joined:
        Jul 15, 2009
        Location:
        WI
        Local Time:
        3:11 AM
        No. The valve is inside the master cylinder port where your line screws in. Looks like a little orfice. If your master is full of fluid, remove the line going to the rear of the car. If no fluid leaks out, it has the valve. Like I stated earlier though, you don't need the valve with new wheel cylinders.
         
        • Thanks! Thanks! x 1
        • Beekeeper

          Beekeeper It’s a disease without a cure! FBBO Gold Member

          Messages:
          4,056
          Likes Received:
          4025
          Joined:
          Jul 4, 2012
          Location:
          Rogersville,TN.
          Local Time:
          3:11 AM
          I’m aware of the newer wheel cylinders having residual valves but I didn’t see any mention of the OP installing new ones.
           
        • khryslerkid

          khryslerkid FBBO Gold Member FBBO Gold Member

          Messages:
          25,734
          Likes Received:
          41112
          Joined:
          Mar 10, 2010
          Location:
          Hanover, Pennslyvania
          Local Time:
          4:11 AM
          Have to ask...are the bleeders at the top on the front calipers?

          Rear shoes adjusted properly, barely dragging to take any play/travel out?

          What brake fluid are you using?
           
          • Agree Agree x 1
          • hunt2elk

            hunt2elk FBBO Gold Member FBBO Gold Member

            Messages:
            8,727
            Likes Received:
            8222
            Joined:
            Jul 15, 2009
            Location:
            WI
            Local Time:
            3:11 AM
            "I then bought the complete rear drum rebuild kit from Doctor Diff with new wheel cylinders"
            Actually too bad he didn't get everything from Cass instead of 3 different places.
             
          • hunt2elk

            hunt2elk FBBO Gold Member FBBO Gold Member

            Messages:
            8,727
            Likes Received:
            8222
            Joined:
            Jul 15, 2009
            Location:
            WI
            Local Time:
            3:11 AM
            Good ideas as well. Rear shoes not adjusted properly will act just like the op is experiencing.
             
            • Agree Agree x 1
            • cbcborm

              cbcborm Well-Known Member

              Messages:
              126
              Likes Received:
              14
              Joined:
              Apr 6, 2011
              Location:
              lakeland,florida
              Local Time:
              4:11 AM
              my problem was basic the same but
              the bleeders were at bottom. air couldn't scape, they need to be at the top on the front calipers.
              I switch calipers position and case solved.
               
            • Beekeeper

              Beekeeper It’s a disease without a cure! FBBO Gold Member

              Messages:
              4,056
              Likes Received:
              4025
              Joined:
              Jul 4, 2012
              Location:
              Rogersville,TN.
              Local Time:
              3:11 AM
              so much for my reading skills:lol:
               
              • Like Like x 2
              • 65_Satellite

                65_Satellite Well-Known Member

                Messages:
                85
                Likes Received:
                111
                Joined:
                Jan 10, 2021
                Location:
                01543
                Local Time:
                4:11 AM
                Yes I mentioned that I bought the complete rear drum rebuild kit including the wheel cylinders from doctor diff
                EB7A4B07-9FEC-491B-891D-2F10427A551E.jpeg
                 
              • 65_Satellite

                65_Satellite Well-Known Member

                Messages:
                85
                Likes Received:
                111
                Joined:
                Jan 10, 2021
                Location:
                01543
                Local Time:
                4:11 AM
                Yes bleeders at the top, rears adjusted with slight drag and using DOT3 7FA8FD73-4BD2-4C61-8A1E-503ADAB4B242.jpeg
                 
                • Like Like x 2
                • khryslerkid

                  khryslerkid FBBO Gold Member FBBO Gold Member

                  Messages:
                  25,734
                  Likes Received:
                  41112
                  Joined:
                  Mar 10, 2010
                  Location:
                  Hanover, Pennslyvania
                  Local Time:
                  4:11 AM
                  What master cylinder did you get?
                   
                • 65_Satellite

                  65_Satellite Well-Known Member

                  Messages:
                  85
                  Likes Received:
                  111
                  Joined:
                  Jan 10, 2021
                  Location:
                  01543
                  Local Time:
                  4:11 AM
                  I had the front disc kit and I did call Cass about the all the lines but the shipping was so costly it wasn’t in the budget.
                   
                  • Like Like x 1
                  • hunt2elk

                    hunt2elk FBBO Gold Member FBBO Gold Member

                    Messages:
                    8,727
                    Likes Received:
                    8222
                    Joined:
                    Jul 15, 2009
                    Location:
                    WI
                    Local Time:
                    3:11 AM
                    How much time did you spend bench bleeding the master? Sometimes it takes quite a bit to get all the air out of them.
                     
                  • 65_Satellite

                    65_Satellite Well-Known Member

                    Messages:
                    85
                    Likes Received:
                    111
                    Joined:
                    Jan 10, 2021
                    Location:
                    01543
                    Local Time:
                    4:11 AM
                    It was part of the kit I bought. It’s a cast iron 15/16 bore C497FEB0-5671-4F0F-9047-707AAEA6E5D9.jpeg
                     
                  • 65_Satellite

                    65_Satellite Well-Known Member

                    Messages:
                    85
                    Likes Received:
                    111
                    Joined:
                    Jan 10, 2021
                    Location:
                    01543
                    Local Time:
                    4:11 AM
                    Maybe about 5 minutes or so. A lot of air bubbles at first and then all fluid. The first master I did in a vice. This is the second one (replacement) and I mounted it to the car and then bled it using the pedal and then attached the lines and bled the system
                     
                  • hunt2elk

                    hunt2elk FBBO Gold Member FBBO Gold Member

                    Messages:
                    8,727
                    Likes Received:
                    8222
                    Joined:
                    Jul 15, 2009
                    Location:
                    WI
                    Local Time:
                    3:11 AM
                    I shouldn't have said that. Just that he is so good about dealing with problems and taking care of you if there is an issue with something he sells. He doesn't stock lines and some other stuff, but has them shipped from The Right Stuff or Inline Tube. So that is why his shipping is higher on some things.
                     
                    • Agree Agree x 1
                    1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
                      By continuing to use this site, you are consenting to our use of cookies.