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Need your thoughts-Rear brakes won't release

Discussion in 'The Hokey Ass Message Board' started by belair, Nov 17, 2012.

  1. belair
    Joined: Jul 10, 2006
    Posts: 8,191

    belair
    Member

    Been putting discs on the 55 Chevy, used a CPP M/C and a Speedway prop. valve. The rear brake cylinders were toast, so I replaced them too. Now the rear brakes will not release unless I open the bleeder valve. What do think is the problem? I have bled the M/C and entire system several times, and can't figure this out unless the M/C or the prop. vale is faulty. Thanks.
     
  2. Somethings holding pressure still. Check to make sure the pushrod is adjusted properly.
     
  3. neverdun
    Joined: Oct 17, 2007
    Posts: 667

    neverdun
    ALLIANCE MEMBER
    1. Maryland HAMBers

    My 32 has power brakes and is doing the same thing. If I disconnect the vacum line it stops hanging up. Not a biggie on such a light car. I sure would like it to stop though. Kills the battery because the brake lights stay on if I don't catch it.
     
  4. Nonstop
    Joined: Jun 18, 2012
    Posts: 175

    Nonstop
    Member
    from CA

    Check the pushrod and the rear flex hose - might be an internal blockage.
     
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  5. belair
    Joined: Jul 10, 2006
    Posts: 8,191

    belair
    Member

    This is not a power brake system.
     
  6. flathead okie
    Joined: May 22, 2005
    Posts: 1,480

    flathead okie
    Member

    rear flex hose has collasped inside = replace it and also replace the front ones if they haven't been replaced.
     
  7. belair
    Joined: Jul 10, 2006
    Posts: 8,191

    belair
    Member

    The rear brakes seem 'reluctant' to move. It is almost like there are two stages of brake acuation. They won't move until a lot of pressure is applied. The rear flex hose has not been relpaced, but the fronts were.
     
  8. "T'RANTULA"
    Joined: Aug 6, 2011
    Posts: 658

    "T'RANTULA"
    Member
    from Ohio

    This is what my problem was when I did the brakes on my 55. Youd be surprised. :eek:
     
  9. L79_Acadian
    Joined: Oct 3, 2006
    Posts: 84

    L79_Acadian
    Member
    from canada

    when the flex hose collapses, the inner hose has a rip in it,so when you put on the brakes,brake fluid pushes the flap of brake hose up, out of the way. This allows the fluid to travel down the flex hose,causing the brakes to apply, but as soon as you release the brake pedal, the flap of brake hose falls down, blocking the return flow for the rest of the brake fluid ( under pressure)from the wheel cylinder to the master cylinder. This causes the brakes to lock up.
    Replace the flex hose, your brakes will be fine then.
    Roger
     
  10. belair
    Joined: Jul 10, 2006
    Posts: 8,191

    belair
    Member

    thanks guys. A new hose it is. The rod adjustment didn't change anything. This car has fought me all the way on this brake deal.
     
  11. 37.5
    Joined: Jul 29, 2006
    Posts: 27

    37.5
    Member
    from mn

    I have had this problem a couple of times, some times the after market proportioning valve has too much resistance for your master cylinder. This may not be your problem, but it only takes about 10 minutes to try....Take the rear fitting out of the proportioning valve. You will find a small spring and a cone shaped piece of rubber. Take them out, re-assemble. See if it works then.
     
  12. 37.5
    Joined: Jul 29, 2006
    Posts: 27

    37.5
    Member
    from mn

    One thing to note, this is if you used the non-adjustable brake proportioning valve same as GM valve used on many cars in the 70's. For disc front/drum rear Speedway part #910-31364.
     
  13. Do you have a residual valve in the rear brake line or built into the master? I'm assuming you used a disc/disc master? Disc/Drum master with built-in residual would hold too much pressure for the disc setup.

    Also, make sure the prop valve isn't installed backward.

    You can crack the line at the master and see if the brakes release. If not, keep cracking the line at each fitting toward the caliper until the brakes release. That will at least tell you where the pressure is being held.
     
  14. belair
    Joined: Jul 10, 2006
    Posts: 8,191

    belair
    Member

    Prop valve, (no residuals) is in the rear brake line. It is a Speedway adjustable type. Thanks for the tip, exwestracer. I will do that.
     

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