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Brakes Tightening While Driving 32 Ford

Discussion in 'The Hokey Ass Message Board' started by Henry VIII, Sep 3, 2009.

  1. Henry VIII
    Joined: Mar 30, 2009
    Posts: 272

    Henry VIII
    Member
    from Tulsa OK

    Newly built 32 Ford Tudor under floor master cylinder pumps up while driving. After about 20 minutes of driving city traffic the brakes are dragging enough that I cannot push the car by hand, but it still drives OK. After sitting a couple of hours+/- the brakes free up but the pedal is lower than normal with barely enough brake to drive safely. The master cylinder rod has been adjusted out twice with no relief. The left side 2 1/2 inch exhaust pipe p***es under the master cylinder with 1 1/2 inches of clearance. The exhaust pipe has been wrapped with DEI wrap, double thickness near the master cylinder. The master cylinder has been wrapped with Kool Mat insulation. Front discs, rear drums, no boost.
    Looking for advice please.
    Al
     
    Last edited: Sep 14, 2011
  2. brokenspoke
    Joined: Jul 26, 2005
    Posts: 2,988

    brokenspoke
    Member

    I had the same problem once...my push rod needed to be shortened....it was causing pressure on master cyl....causing heat build up , with caused brakes to lock up
     
  3. Ghost28
    Joined: Nov 23, 2008
    Posts: 3,192

    Ghost28
    Member

    It doesn't have to be just the master cylinder. Any brake line that is to close to a heat source can cause this problem. I do agree with the response about shortening the push rod, and not making it longer or tighter. Cause if your fluid is gettin hot it will expand and the tighter push rod will have no relax area and will act as your foot and activate your brakes...John
     
  4. there are little ports in the MC that allow brake fluid to return to the reservoir. they are uncovered when the piston is all the way out....when you push down on your brake pedal the piston inside covers them up. so either the piston is not coming all the way out because of mis-adjustment of the push rod , or the little holes are plugged with ****
     
  5. Henry VIII
    Joined: Mar 30, 2009
    Posts: 272

    Henry VIII
    Member
    from Tulsa OK

    Thanks, I was beginning to wonder if the holes might be plugged.

    Al
     
  6. pasadenahotrod
    Joined: Feb 13, 2007
    Posts: 11,772

    pasadenahotrod
    Member
    from Texas

    IS your wrap around the cylinder closing off the cap vent?
     
  7. Henry VIII
    Joined: Mar 30, 2009
    Posts: 272

    Henry VIII
    Member
    from Tulsa OK

    Thanks, I'll have another look at the plumbing. The adjustments that we've made have effectively shortened the rod quite a bit. Will take another look into this.
    Al
     
  8. sixpac
    Joined: Dec 15, 2002
    Posts: 553

    sixpac
    Member
    from Courtenay

    We had a brake pedal that wasnt returning all the way and it was doing the same as yours.
    There was a brake pedal stop on the return.
     
  9. Henry VIII
    Joined: Mar 30, 2009
    Posts: 272

    Henry VIII
    Member
    from Tulsa OK

    Good question, but after adding the wrap there seemed to be no change, better or worse.
    I'll check this out further.

    Al
     
  10. Henry VIII
    Joined: Mar 30, 2009
    Posts: 272

    Henry VIII
    Member
    from Tulsa OK

    I don't think that's the problem but will check.

    Al
     
  11. Limey Steve
    Joined: Apr 4, 2005
    Posts: 1,522

    Limey Steve
    Alliance Vendor
    from Whittier

    You need a return spring on the pedal , then you need to set 1/16 to 1/8 freeplay at the push rod when the pedal is returned via the spring. do you have residual pressure valves installed ? if so are they the right way around ? you could be pressurizing the m/c not the wheel cylinders if they are in backwards. My 2c.
     
  12. Henry VIII
    Joined: Mar 30, 2009
    Posts: 272

    Henry VIII
    Member
    from Tulsa OK

    Hmmm... no spring on the pedal. I'll have to check the residual pressure valves. But the brakes do work good enough to drive.
    Thanks, you've given me some things to check. I'm the owner but not the primary builder.

    Al
     
  13. Limey Steve
    Joined: Apr 4, 2005
    Posts: 1,522

    Limey Steve
    Alliance Vendor
    from Whittier

    Also did you adjust up the rear brakes with a little drag when cold ? often forgotten & must be done to bleed brakes correctly & get a proper pedal .When it is dragging check the front & rear to see which end or both are binding , narrow down the problem that way too .
     
  14. Henry VIII
    Joined: Mar 30, 2009
    Posts: 272

    Henry VIII
    Member
    from Tulsa OK

    I think we're good there but will check.
    Thanks again.

    Al
     

  15. Precisely...!

    I had the exact same problem

    It has to fully release to work and recheck your return spring to see if there's enough "PULL" to return the pedal all the way back.
     
  16. Big Mac
    Joined: Sep 12, 2007
    Posts: 1,565

    Big Mac
    Member

    I had this exact same problem too. Turned out it was the wrong pushrod for the master cylinder. Needed a shorter one. Try that, it's an easy fix.
     
  17. Limey Steve hit on it with his lack of freeplay comment.

    After you install a return spring you should have 3/8"-1/2" free play.
     
  18. tommy
    Joined: Mar 3, 2001
    Posts: 14,756

    tommy
    Member Emeritus

    Free play with a return spring. Sometimes the weight of the pedal can apply enough pressure to take up all the free play and keep the piston from returning that last little bit. The return spring takes the weight of the pedal off of the piston. The spring inside the M/cyl. is not enough. All cars have pedal return springs just for this reason. It's critical in an the under the floor M/cyl. system.
     
  19. Residual valves can only be used with drum brakes . If you have a residual valve in the line to the disc brakes it will cause them to drag. Keith
     
  20. Henry VIII
    Joined: Mar 30, 2009
    Posts: 272

    Henry VIII
    Member
    from Tulsa OK

    I appreciate all of the comments. Now I have several things to check and/or correct.
     

  21. ummm, no. you use a 2lb for disc when the master is lower then the caliper (like under the floor) and a 10lb for drums.

    i also agree with needing a pedal return spring and then setting up the free play.
     
  22. Limey Steve
    Joined: Apr 4, 2005
    Posts: 1,522

    Limey Steve
    Alliance Vendor
    from Whittier

    I'm sure you mean 3/8 to 1/2 freeplay at the pedal NOT the pushrod !!:confused:
     
  23. Henry VIII
    Joined: Mar 30, 2009
    Posts: 272

    Henry VIII
    Member
    from Tulsa OK

    I'm pretty sure the cap vent is clear, the wire latch is holding the wrap up off most of the cap.

    I've added some wrap around the MC to cover the brake lines as they enter the cylinder.

    There is a blue color coded residual valve on the disc brakes and a red coded one on the drums. They are clearly marked for directions and are installed correctly.

    I'm now working on a return spring and a place to anchor it. The pedal is heavy and the weight takes up all of the slack. I think the slack is about the right amount when I pull the pedal up.

    Al
     
    Last edited: Sep 4, 2009

  24. Corect.

    Thanks:)
     

  25. Here's one way.
    [​IMG]

    [​IMG]

    [​IMG]

    You'll need a pedal stop so there is no possibility of the rod dropping out.
    [​IMG]

    This one is adjustable.


    The threaded rod shown is a cut-down standard Ford M/C rod

    M/C is a dual chamber Mustang with 7/8" bore.
    (Goes to 68-70 Mustang discs - 11" rotor - and 11" 68 Mercury wagon drum brakes in rear.


    The one shown is in my 31 on 32 frame roadster project.

    I have an identical spring setup in my 32 and its been doing fine for 15 years and 50,000 miles.
     
  26. Henry VIII
    Joined: Mar 30, 2009
    Posts: 272

    Henry VIII
    Member
    from Tulsa OK

    Nice piece of work. I had not thought of a compression spring.

    My pedal is stopped by the lower part of the firewall. I don't think it is possible for the rod to pop out but I'll make sure.

    Thanks for the pictures.
     
  27. Limey Steve
    Joined: Apr 4, 2005
    Posts: 1,522

    Limey Steve
    Alliance Vendor
    from Whittier

    Nice stuff C9,, this is a quality thread , how the HAMB should be .
     
  28. Regardless of the problem.......................Get rid of the Aluminum residual valves! We have had many discussions here about how bad they are or will be down the road. I prefer the Br*** ECI valves. The old shop I worked at had a small drawer of cracked and beat up anodized Speedways and Wilwoods gathering dust.
     
  29. ECI or one of their dealers. Ralph from ECI is on the HAMB, search my brain addled primate pal:D;):)
     
  30. It seems the Aluminium ones split out from the pipe thread and rely on a tight seal.Br*** holds up mucho better. Serious, search "residual"
     

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