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Technical Brake issues

Discussion in 'Traditional Hot Rods' started by gasservette68, Jul 12, 2018.

  1. gasservette68
    Joined: Feb 7, 2010
    Posts: 64


    Ok so ive got a '29 A ive got an under the floor master, wilwood prop valve and 10 lbs residual valves early 39 drums up front and later bendix style in the rear and it stops good enough. After i drive a bit itll feel like im draggin a boat and the pedal will get really hard. Sometimes itll let go sometimes not and when its taken on this behavior itll leave the brake lites lit l. the brakelite switch is on the prop valve just off the master. If it sits the condition will subside. Hard to tell if its draggin all 4 when its doing it. Im so irritated when i get home i havent jacked it up and spun em. I suspect a bad rubber line swelling but everything is new.. Any suggestions before i just tear it apart. Thanks
    P.S. i dont have a return spring on the pedal but when it builds this pressure the pedals all the way out. It seems somethings swelling or ???
  2. studebaker46
    Joined: Nov 14, 2007
    Posts: 688


    usually this s caused by no free play in brake pedal. shorten rod that goes into m/c what happens is brakes are staying partially engaged ,hence the brake lite staying on. May have to install return spring tom
    Unkl Ian likes this.
  3. sunbeam
    Joined: Oct 22, 2010
    Posts: 5,330


    Crack a bleeder to see which end the problem lies. Which end is the brake switch assuming it's hydraulic?
  4. KJSR
    Joined: Mar 7, 2008
    Posts: 2,468

    from Utah
    1. Utah HAMBers

    Pedal rod adjustment.....

  5. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,773

    V8 Bob

    You always NEED a pedal return spring, and about 1/16" free play in the input rod to the master cylinder.
  6. alchemy
    Joined: Sep 27, 2002
    Posts: 17,251


    Yes, you NEEEEEED a return spring and a couple hairs of clearance from the rod to the plunger.
  7. gasservette68
    Joined: Feb 7, 2010
    Posts: 64


    A friend os mine suggested cracking the bleeder my brake lite switch is up front on the prop valve i tgink my problem lies in the front.. Im gonna look into the free play first its strange it creeps on after ive been driving a bit..thanks
  8. chargin03
    Joined: Jan 8, 2013
    Posts: 499


    Had a new residual valve that gave me the same problem.
  9. 100% Matt
    Joined: Aug 7, 2006
    Posts: 2,638

    100% Matt

    What master are you using and what's the pedal assembly?
  10. Mr48chev
    Joined: Dec 28, 2007
    Posts: 30,030


    master-cylinder.png master-cylinder.png A little explanation on what the guys are saying.
    With no return spring the weight of the pedal assembly puts a bit of pressure on the brakes. The spring pulls it back so there will be just a little freeplay between the push rod and the piston.
    The adjusting the push rod, same thing, you have to have that bit of free play or it can push the piston just enough to cover the return port between the cylinder and the reservoir not letting the fluid go back in.
    Last edited: Jul 12, 2018
    Hnstray likes this.
  11. gasservette68
    Joined: Feb 7, 2010
    Posts: 64


    Ok so last nite i adjusted the rod back until ive got the slightlest play but it was late ive gotta take the car around town as the problem comes on after driving a bit i can see that theres some movement in the pedal before the lites lite up so its not holding pressure the way it was but as i said after a quick run lets see. As for the return im goin to install/make one but im running a later style master and i mention that because on later cars ive never seen a return spring i can see where it cant hurt but i guess i assumed they were build in the later style mast cyls.. Thanks for the help ill let u know in a day if ive made any progress in regard to the free play i can tell u i was snug on the master i dont remember setting it up that way when i did the brake system. Thanks again
  12. wuga
    Joined: Sep 21, 2008
    Posts: 397


    I encountered the same situation and found after an extensive search that the push rod was nor exactly 90 degrees to the piston and would drag slightly on the rim of the M/C and after a short while keep the brakes applied. I would open a bleeder and it went but always returned until the M/C was squared.

  13. Petejoe
    Joined: Nov 27, 2002
    Posts: 11,071

    from Zoar, Ohio

    Another thing to consider....
    Is your exhaust close to your master cylinder?
    I’ve had to wrap one with heat tape to prevent the MC from getting hot and expanding the fluid.
    ClayMart and dirt t like this.
  14. 100% Matt
    Joined: Aug 7, 2006
    Posts: 2,638

    100% Matt

    The reason I asked what MC you’re running is there are a few with built in residual valves... if you’re running one with an additional residual valve inline that could be your issue

    Sent from my iPhone using The H.A.M.B. mobile app
  15. Nemosgarage
    Joined: Sep 21, 2009
    Posts: 135


    My residual check valve failed and caused the same problem.
  16. BJR
    Joined: Mar 11, 2005
    Posts: 7,143


    It also can be a brake hose failing. If it's only one front or both rear wheels, check the rubber brake hose going to that wheel. When they fail the inside comes apart and acts as a one way valve. It lets the fluid under pressure go to the brake, but not back to the master cylinder.
    100% Matt likes this.

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