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Technical Master Cylinder Issue

Discussion in 'The Hokey Ass Message Board' started by phoenix5x, Apr 22, 2020.

  1. winduptoy
    Joined: Feb 19, 2013
    Posts: 2,945

    winduptoy
    ALLIANCE MEMBER

    So, some master cylinders have a residual valve internally... the reason for a residual valve is to hold the shoes a little closer to the drum to limit pedal travel in a brake application.
    Lets say the master cylinder has a internal valve and there is a external valve added.
    I say loose the rear brake residual valve and see what happens...I believe 10 psi is too much thinking out loud and you master cylinder may already have a residual valve in that circuit
     
  2. Wrong, the residual valve is to keep air from coming past the wheel cylinder cups upon brake release. And 10 psi is good for drum brakes.

    This is all false.


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    Montana1 likes this.
  3. winduptoy
    Joined: Feb 19, 2013
    Posts: 2,945

    winduptoy
    ALLIANCE MEMBER

    RESIDUAL+CHECK+VALVE+disc_rear+drum+brakes..jpg Boy since you are the hall monitor, you need to be careful about falsely stating that this is all false.
    So if he has a residual valve in line and a residual valve in the master cylinder is my major point.
    Also there is no cup to hold against the piston wall in a disc brake and it is uncommon to use one on a disc application.
    I stand corrected on the original basis for a residual valve...though that has changed over the years. However I am questioning if his master cylinder is a equipped with a residual valve AND an inline valve plus having a residual valve on the discs
    I have no idea what he has
    CheckValve.jpg
     
  4. I’m sorry, it was all false, like it or not, if he has two residual valves I don’t think it would make any difference at all, it’s strictly a one way check valve. You only need a two pound residual valve on disc brakes if the master is below the calipers but it won’t hurt anything.

    The purpose on drum brakes has not changed over the years, sorry again. They were phased out with the advent of cup expanders in wheel cylinders.

    Please tell me what part I was wrong stating it was false?


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  5. phoenix5x
    Joined: Dec 26, 2007
    Posts: 241

    phoenix5x
    Member
    from Ohio

    Hey all sorry for delay in response life got,in the way...i re plumbed the front resevoir to the rear and the rear resevoir to the front and all is well...i am guessing it has to do soemthing with the spring pressure but its working fine now..thanks all for the info..very informative

    Sent from my VS995 using The H.A.M.B. mobile app
     
    pbr40, David Gersic and swade41 like this.
  6. Well there you go...now I’m on a mission to find out why...

    Glad you got it fixed


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  7. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 10,800

    Johnny Gee
    Member
    from Downey, Ca

    And that's why I said what I said in post #70. I bet if you had bleed the front brakes first with how you had it plumbed before all would have been well. You were try to bleed secondary prior to doing primary end of master. But want does brake fluid care.
     
  8. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,878

    V8 Bob
    ALLIANCE MEMBER

    Could it be the fluid volume difference between the primary and secondary? ;) Just pokin' the bear. :)
     
    Desoto291Hemi likes this.
  9. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,878

    V8 Bob
    ALLIANCE MEMBER

    It doesn't matter the bleeding sequence with a dual master cylinder; primary first or secondary, front or rear axle.
     
    Desoto291Hemi likes this.
  10. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 10,800

    Johnny Gee
    Member
    from Downey, Ca

    ^^^^^ Did OP ever say he never got a pedal? Reread post #1. OP doesn't understand what he's feeling while bleeding. Then find post where OP states master was a working unit from a donor vehicle. As most do they'll start at the back then work forward when bleeding. That's text book 101 single circuit ideology. Sure one can bleed the other way around. But understand what going's on and why. Again, as @31Vicky with a hemi has said...
     
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  11. Just as long as it’s perpendicularly parallel while remaining level to the intersecting slope.
    Oh wait that is driveline angles My bad.
    What’s this one about again? :D
     
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  12. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 10,800

    Johnny Gee
    Member
    from Downey, Ca

    The affect's of thrusting and exchanging of fluids from one to the other. Oh wait, wrong tab was open. ;):p:D
     
    31Vicky with a hemi likes this.
  13. nobby
    Joined: Jan 8, 2006
    Posts: 898

    nobby
    Member

    so.... does a 1968 or 1976 mustang have these expanding sealing cup
    what is actually 'modern'
    when was the article written
     
  14. boo
    Joined: Jul 6, 2005
    Posts: 574

    boo
    Member
    from stuart,fl.

    TODAY, my friend and i were trying to find why i couldn't beleed my rear brakes, a 1967 mustang mc mine is early ford hyd bks, so i need a drum,drum MC, both resivors the same size. the MC i have was a new one made in china, the front piston was froze up, rong size cups, Oh! the fromt line goes to rear brakes, if it was mounted on firewall.
     
  15. the flatlander
    Joined: Apr 29, 2004
    Posts: 615

    the flatlander
    Member

    The one with the 'Vette master has it right: large res. to front discs. After many tests with similar & worse problems we (@ my shop) never used propor. valves if running larger tires on rear. Really ! And we never used Chinese residual pressure valves. Try it (if still problems) removing the porpr. valve. They are each designed for diff. weight & configuration of vehicles. & try it ! good luck The off the ground check is a good idea too. :)
     
    Montana1 and Johnny Gee like this.
  16. Really hard to know without taking it apart and looking for the cup expanders, the cup seals are the same there will be a metal disc between the spring and seal or the end of the spring will be wound in a taper that fits inside the seal


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  17. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 10,800

    Johnny Gee
    Member
    from Downey, Ca

    That's all I've ever done. Not saying it works for all applications. Sure in hell works with 165 15 to 235 thru 295 15 combo's.
     
    Montana1 likes this.

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