Help too much travel in brake pedal!!

Brakes, Steering & Suspension

  1. Just wheels

    Just wheels Active Member

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    Have '66 Coronet.
    Had manual drums
    Converted to power and front discs
    All new parts from Pirate jack including proper master cylinder, proportioning valve/metering valve. booster.
    Checked plumbing, all plumbed correctly.
    Brakes have been fully bled (multiple times, now at brake shop and he bled again)
    Car stop perfectly

    But pedal goes almost to floor before engaging brakes. Car stops when pedal is about 1/2 and inch off the floor. There seems to be no brake engagement for the first 2-3 inches of brake pedal travel

    UGH!

    Anyone know the fix?
     
  2. 440+6

    440+6 FBBO Gold Member FBBO Gold Member

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    Did you adjust the rod from the booster to the master cylinder?
     
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    • Just wheels

      Just wheels Active Member

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      I did not, but the shop it is at now tried it, just a little and the back brakes locked up
       
    • black64

      black64 FBBO Gold Member FBBO Gold Member

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      I believe the pedal ratio is different from manual to power brakes this could be a reason. Also if the bleeders on the calipers are at the bottom instead of the top there could be air trapped.
       
    • Just wheels

      Just wheels Active Member

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      Put the power brake linkage at pedal as well, that's required, is that the ratio you are referring to? I'll check bleeders.
       
    • Just wheels

      Just wheels Active Member

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      Bleeders at top. Frustrated.
       
    • RT K_line

      RT K_line Well-Known Member

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      How does the parking brake engage. I usually push the pedal down 3 clicks then adjust the rear shoes untile there is some drag when spinning the tire, other than that, the master may not displace enough fluid. I have read some threads that said there are different size pistons in the master.
       
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      • 440+6

        440+6 FBBO Gold Member FBBO Gold Member

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        Make sure your rear brakes are adjusted properly, too much play can cause allot of pedal travel
         
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        • dvw

          dvw Well-Known Member

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          Vice grip all 3 rubber flex lines. Is the pedal good? If so you have to much pad travel,shoe travel, or air in the system at the wheel. Take one vice grip off at a time to find the culprit. If the pedal is still low with the vice grips you either have the wrong pedal ratio or too small a master cylinder bore.
          Doug
           
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          • Just wheels

            Just wheels Active Member

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            All good ideas, thanks dvw, 440+6 RTK and others. Will try these. MBM/Pirate Jack site also recommends bleeding the calipers off the mount, tilting the bleeder to top to make sure no air gets trapped.
             
          • bc3j

            bc3j Member

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            Just a thought, was the master cylinder bench bled?
             
          • black64

            black64 FBBO Gold Member FBBO Gold Member

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            If bleeders are at the top and pedal ratio is correct next thing is does your master cyclinder have residual valves for the rear brakes usually 10 psi for drums and 2 psi for disk? Most have residual valves in them but might want to make sure on the master part number you have.
             
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            • MoparMikey

              MoparMikey Well-Known Member

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              The master supplied has too small of a bore. Increasing bore size decreases pressure/increase fluid moved and the pedal travels less distance to do the same amount of work. As an example, on Chevys with large front calipers (2 15/16" pistons) going from a 1" bore master to 1 1/8" bore master will raise the pedal about an inch and a half when engaged.
               
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              • Kern Dog

                Kern Dog FBBO Gold Member FBBO Gold Member

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                You can buy pipe plugs to block off the brake lines at the master cylinder. This keeps all fluid and pressure in the master cylinder itself. Firm pedal? The problem lies downstream either with the lines, the calipers or the rear brakes.
                Oh, are the wheel bearings properly adjusted? Loose bearings allow more movement of the calipers.
                 
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                • Just wheels

                  Just wheels Active Member

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                  Pirate Jack sent new Master Cylinder and Proportioning valve/metering valve. Going to try the new master cylinder first, then work my way through the suggestions. Thanks for all you help!
                   
                • rrTor-Red

                  rrTor-Red FBBO Gold Member FBBO Gold Member

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                  I was just going to ask that question myself. That would be the starting point. Air can be still trapped in the M/C where as the pedal travel can't expel all of the air. That's why they say to bench bleed them FIRST and push piston all the way in.
                   
                • Derwud

                  Derwud Well-Known Member

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                  Did we get it fixed??
                   
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