66 Sat upgrade to front disc brakes

Brakes, Steering & Suspension

  1. Pa's Sat

    Pa's Sat Member

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    I changed out the drum for disc brakes on front and kept the drums on the back. Got a new master cylinder with booster and portion valve setup from Classic. I bench bled the clyinder several times and the lines several times and still don't have good brakes. When first pushing the pedal down I feel some braking but as the pedal goes down it looses power and have to push very hard to get any braking. The pedal also does not pump up to a solid feel with the engine off. The vacum is 12-15 lbs.
    After the brakes are working it is off to the body shop and then paint.
    Any suggestions and help is needed and welcome. Thanks for all or any ideas.
     
  2. 4mulas

    4mulas Well-Known Member

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    How and in what order did you bleed the lines. And the master.

    What master cylinder did you get exactly?
     
  3. Pa's Sat

    Pa's Sat Member

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    I got P/N MN5007 from Classic and followed the directions to bench bleed and did that twice just to be sure and then bled the lines from rt rear, left rear, rt front and left front several times when not getting a good brake pedal. Did not disconnect the proportioning valve from master if that makes a difference.
     
  4. Don Frelier

    Don Frelier FBBO Gold Member FBBO Gold Member

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    Are the bleeders on the front calipers at the highest point? They can sometimes be installed in reverse.
    No leaks?
     
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    • dan juhasz

      dan juhasz FBBO Gold Member FBBO Gold Member

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      any pictures
       
    • 4mulas

      4mulas Well-Known Member

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      How did you bench bleed the master if you did not disconnect the Proportioning valve from it?
       
    • BB BELLA

      BB BELLA Well-Known Member

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      are the rears adjusted up firm! I know on my dually if the rears get loose the fronts don't work worth shit!
       
    • Pa's Sat

      Pa's Sat Member

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      Here is pictures of setup and caliper. The rear brakes will start to grab and then releases as the pedal goes down. Did on gravel to find out which wheels were grabbing. There are no leaks. Put this on over a year ago so don't remember if I did or did not take off proportioning valve for sure. Would that be a place to try again?

      DSCN7788.JPG DSCN7787.JPG DSCN7786.JPG
       
    • 4mulas

      4mulas Well-Known Member

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      I would start from scratch.
      -Master bench bleed by itself
      -hook ups provalve
      -bleed brakes RR, LR, RF, and the LF last.
      -repeat if necessary.
      -report results

      Those calipers may be somewhat difficult to bleed too as the bleed screw is right near the inlet. Leaving a large area above all of that for air to be potentially trapped.
      take your time bleeding
       
    • Don Frelier

      Don Frelier FBBO Gold Member FBBO Gold Member

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      I believe the caliper orientation is your problem. There's no way to get the air out of the caliper. You can either swap sides or unbolt and tip upwards so the bleeder screw is the highest point. Put block of wood where the rotor would normally be and bleed them. Rear brakes likely are fine. I think your problem will be solved.
       
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      • Ernie ingling

        Ernie ingling Well-Known Member

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        Yep calipers on wrong switch sides for a start.
         
      • dan juhasz

        dan juhasz FBBO Gold Member FBBO Gold Member

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        yep your calipers need to be switched left to right
         
      • 4mulas

        4mulas Well-Known Member

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        Swapping those calipers side to side is a bad idea. That would put the fluid inlet above the bleeder screw.
        These calipers are an older design and can work but in that configuration have been known to cause some bleeding issues. The one idea from @Don Frelier of removing it, putting a block of wood between the pads, orienting the bleeder screw to the highest point and bleeding is a good one.

        The earlier calipers had the inlet and bleed on the same side of the piston. In the future order ones from a mid eighties diplomat where the inlet and bleeder are opposed.

        I’m still curious if you tried to bench bleed the master with the proportioning valve on?

        This is an example of the diplomat caliper
        01A79CC2-6618-493B-94CD-505187B59657.jpeg

        This is close to what you have (early 73-77 or so A body calipers), air could potentially get trapped in the red area I circled
        1BB9AF85-684E-4F29-BDD5-EA97A9399924.jpeg
         
        Last edited: Jan 19, 2020
      • dan juhasz

        dan juhasz FBBO Gold Member FBBO Gold Member

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        No disrespect , but just switch sides on the calipers and you will be golden
         
      • andyf

        andyf Well-Known Member

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        You have a caliper problem. Either the wrong calipers or they are on the wrong side. Can't tell without more pictures. Hose routing looks wrong too. Very common problem, lots of people just assume that anything will bolt on to anything but it doesn't. They actually made different parts for different cars.
         
      • Pa's Sat

        Pa's Sat Member

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        The calipers do not switch sides or the hose will be on the outside of the disk. I started from scratch and bled all of the system-bench bleed master cylinder, etc. Ended up that the calipers were holding air and had to take them off, tip them so the bleeder valve was above the inlet hose, got the air out and all is good. Thanks for all the ideas and thoughts about my problem. Now the car is ready to go to the body shop for a quarter panel, then back home to prime and make sure it is ready for the final paint.
         
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