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Technical Brake Issues

Discussion in 'Traditional Hot Rods' started by Steve20, Aug 10, 2019.

  1. Steve20
    Joined: Jan 14, 2017
    Posts: 15

    Steve20

    Hopping for some help. I have an on going issue with my brakes.
    They are traditional manual brakes, with drums on rear disks on front (no booster). Wilwood master cylinder.
    The pedal continues to go soft. I bleed the air out of the fronts and its fine for a week or so then goes soft and need to be re bled. There is no signs of a leak anywhere and I don't seam to be losing fluid.
    I changed the front flex lines and that seamed to fix the problem for about a season and a half but its doing the same thing again. I am using regular DOT3 fluid.
    Is there a chance that the fluid is eating the rubber in the hose??
    Any other thoughts?
    Any help appreciated
     
  2. AngleDrive
    Joined: Mar 9, 2006
    Posts: 1,145

    AngleDrive
    ALLIANCE MEMBER
    from Florida

    Manufacturer of front calipers and rotors?
     
  3. Steve20
    Joined: Jan 14, 2017
    Posts: 15

    Steve20

    They are an 80's GM (Monte Carlo I believe)
     
  4. Black_Sheep
    Joined: May 22, 2010
    Posts: 1,446

    Black_Sheep
    Member

    Master cylinder under the floor?
    Are you using residual pressure valves?
     

  5. Steve20
    Joined: Jan 14, 2017
    Posts: 15

    Steve20

    They are 80's GM (Monte Carlo I believe)
     
  6. Steve20
    Joined: Jan 14, 2017
    Posts: 15

    Steve20

    The master is under the floor and yes residual valves for front and rear. also a proportioning valve for the rear
     
  7. Rear hose?Bad seals on wheel cylinders?
     
  8. Torana68
    Joined: Jan 28, 2008
    Posts: 1,415

    Torana68
    ALLIANCE MEMBER
    from Australia

    If you are only getting bubbles out of the front (?) you are sucking air somewhere in the front system, re tighten everything and see how you go.
     
  9. Steve20
    Joined: Jan 14, 2017
    Posts: 15

    Steve20

    I only get air bubbles when bleeding the fronts. The master is a Wilwood unit with front and rear chambers. Each chamber has its own screw on type cap. Is it possible that air could be pulled in past a seal in the cap??
     
  10. alchemy
    Joined: Sep 27, 2002
    Posts: 20,404

    alchemy
    Member

    In reading brake threads here lately I've seen a couple guys who discovered their problem was a poor flare or seal. It was letting air into the system in very small quantities, and not leaking any fluid out. I found this hard to believe, but when they found and fixed it, their problem went away. How could more air get into the system without causing the fluid to be removed?

    Anyway, I would recommend tightening every joint and fitting in your system. And pay real close attention to see if any are seeping. That might be the only way you discover a very minute leak.
     
  11. Steve20
    Joined: Jan 14, 2017
    Posts: 15

    Steve20

    I thank you all for your responses.
    I bled the brakes again this morning and got out at least one full pump of air. Once again the pedal is nice and hard.
    I have tried re tightening all fittings in the past, so at this point i think I'm going to re plumb from the master out to each wheel.
    Hopefully I can then put this behind me. Nothing worse than looking at a ride you can't use.
     
  12. AngleDrive
    Joined: Mar 9, 2006
    Posts: 1,145

    AngleDrive
    ALLIANCE MEMBER
    from Florida

    Check the runout on the front rotors. You might not feel it braking but you still could have some. I have experienced air getting into calipers on corvettes with runout. It vibrates the piston when no pedal pressure is applied. Never had it with a single caliper piston but you never know.
     
  13. Steve20
    Joined: Jan 14, 2017
    Posts: 15

    Steve20

    Thanks.
    I have never heard about runout. I'll definitely take a look for that
     
  14. chevyfordman
    Joined: Oct 4, 2008
    Posts: 1,354

    chevyfordman
    Member

    I put pressure on the system once for awhile, eventually the leak showed up with one drop. Finally cured my problem. If you are using a vacuum pump, remove the bleeder and wrap it in Teflon tape and make sure the bleeder hose goes straight up from the bleeder plug.
     
  15. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 12,600

    Johnny Gee
    Member
    from Downey, Ca

    How well are the rear shoes adjusted? Never mind which way master is pointing. Which chamber of master feeds what?
     
  16. IRION29
    Joined: Feb 25, 2013
    Posts: 60

    IRION29
    Member
    from Alberta

    As Johnny G points out compartments could be reversed. Was the M/cyl.bench bled?
     

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