Register now to get rid of these ads!

What am I doing wrong? (Brake Question)

Discussion in 'The Hokey Ass Message Board' started by Shaun1162, Jun 30, 2013.

  1. Shaun1162
    Joined: Feb 22, 2010
    Posts: 833

    Shaun1162
    Member

    I hate to post another thread on brakes, but after going through numerous other threads about brakes, my head is spinning...

    I'm trying to figure out where I went wrong with the brake system on my '33 Ford that was an old stock car..

    Has '42-'48 Ford brakes all around (new wheel cylinders, shoes, drums turned, lines, and hoses).

    The master cylinder on the car was a single pot GM style. When I ran the part number cast on the bottom, it came up with either a single or double. I thought I'd make a smart move and go with the dual resevoir master cylinder. This MC was used on a variety of (mostly) GM vehicles and the late 60's early 70's, so I assume that it is set-up for drum/drum applications. Here is a link to it: http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?R=NMAM2040_0332904800 It has a 1" bore. It is mounted in the firewall and higher then the everything else.

    I plumbed everything with 1/4" brake line. No visible leaks. Bench bled the MC, installed it, and then vacuum bled the lines. Had problems with soft pedal, so I had someone else help me bleed the brakes today. Got a little bit of air, but even after bleeding them again I have little pedal.

    The brakes are all adjusted, maybe even dragging a little too much (to be sure that wasn't the problem).

    I've tried adjusting the pushrod quite a bit in and out, but I'm not sure how much freeplay there should be? I've heard 1/16"...

    Seems like everyone had their own opinions on residual valves, but seeing as how this MC was used on drum/drum cars, I assume they're built right into it? I did not plumb in any external ones residual valves.

    Could it be a defective MC?

    Appreciate any advice you guys can give... The rest of the car is pretty much done, but the brakes are haunting me!
     
  2. willys1
    Joined: Oct 31, 2012
    Posts: 1,021

    willys1
    Member
    from South Ga

    You can block (fab some plugs) off the master cylinder where the lines attach, and, with no air in the cylinder the pedal should be rock hard and high. Also make certain that you have free play in the actuator rod to the cylinder. The piston must return to the base of its bore or you will trap air. Depending on how you are bleeding the system: If the system was empty(assumption) and you pump the pedal fast as some people insist on doing, you will make large air bubbles into millions of small air bubbles therefore requiring a lengthy bleeding session. Anyone with a power bleeder is your area? These are just basics to think about. When something is kicking my a$$ I generally return to basics and fix the problem. :)
     
  3. willys1
    Joined: Oct 31, 2012
    Posts: 1,021

    willys1
    Member
    from South Ga

    Forgot to explain : blocking off the cylinder with plugs will prove or disprove your question on a bad cylinder.
     
  4. repeater
    Joined: Aug 20, 2012
    Posts: 60

    repeater
    Member

    I had a similiar situation on my '55 Willys. Same situation, all new everything and converted the fronts to disc brakes, so everything was new. I bled those things for 30 minutes and still had a soft pedal. I gave up, came back the next day and bled again, and on the first bleeder I popped open, I had air. Bled thoroughly again and finally the pedal was good. Sometimes air just manages to hang in there somewhere. Even sometimes when I use a power bleeder is still doesn't help. Some people crack the lines open and gravity bleed it all day, adding fluid slowly...sometimes the walking away and come back tomorrow works (worked for me).
     

  5. JohnEvans
    Joined: Apr 13, 2008
    Posts: 4,883

    JohnEvans
    Member
    from Phoenix AZ

    more than good chance it does NOT have residual checks in it. 1" is alittle small as stock Ford was 1-1/16" but should work. Will your pedal stroke the MC full travel? If not that may also be some of the problem as pedal ratio is wrong. Manual brakes need 2 things pedal wise right ratio[5-6 to1] and enough travel to fully stroke the MC.
     
  6. carlos
    Joined: May 2, 2005
    Posts: 1,382

    carlos
    Member
    from ohio

    Drum drum will have the same size resivor,disc drum one is larger
     
  7. Your lines are too big....go to 3/16
     
  8. Shaun1162
    Joined: Feb 22, 2010
    Posts: 833

    Shaun1162
    Member

    Thanks for the advice guys

    Worked a little more on it today... I re-adjusted the push rod and made sure that the piston returns fully- no improvement.

    Found the fitting for the front brakes was a little loose, fixed that, secured the line better, and then bled all the lines agin- got quite a bit of air out of the front, but still have to pump pedal, and it'll still go to the floor if I push it enough.

    The push rod will bottom the piston out, so I think that's alright. Will have to try to check the ratio??

    Weren't all Ford brake lines 1/4"? I realize my MC is a tad smaller, but can't see where that would make a huge difference...
     
  9. Ole don
    Joined: Dec 16, 2005
    Posts: 2,915

    Ole don
    Member

    Yes, the older Fords used a larger brake line diameter. If part of your new line goes up, air will trap at the top.
     
  10. 73super
    Joined: Dec 14, 2007
    Posts: 778

    73super
    Member

    I agree with "going back to basics" thing.. Always start bleeding with brake farthest from MC and work your way up. My bet would be air in the system.. Make sure you're bleeding in proper sequence.. (Although rarely do I follow my own advice).
     
  11. Gene Boul
    Joined: Feb 9, 2006
    Posts: 805

    Gene Boul

    As above...block off the MC to prove or disprove the Integrity of the unit. When you completely block off the MC it will be rock hard, if not thats your problem. My guess is you still have air trapped in the system...
     
  12. VoodooTwin
    Joined: Jul 13, 2011
    Posts: 3,455

    VoodooTwin
    Member
    from Noo Yawk

    Did you adjust the front brake shoes? I ask because I had the same issue. As soon as I adjusted the shoes, I got a wicked firm pedal.
     
  13. Dreddybear
    Joined: Mar 31, 2007
    Posts: 5,996

    Dreddybear
    Member

    ???
     
  14. JohnEvans
    Joined: Apr 13, 2008
    Posts: 4,883

    JohnEvans
    Member
    from Phoenix AZ

    Line size has NO bearing/efect on brake operation !
     
  15. Dreddybear
    Joined: Mar 31, 2007
    Posts: 5,996

    Dreddybear
    Member

    Line size makes no difference.
     
  16. Dreddybear
    Joined: Mar 31, 2007
    Posts: 5,996

    Dreddybear
    Member

    What this guy says.
     
  17. Shaun1162
    Joined: Feb 22, 2010
    Posts: 833

    Shaun1162
    Member

    OK, didn't think the line size would make any difference...

    Went through the bleeding process yet again... Bleeding from the farthest wheel from the MC first, etc.

    Got some air out of the driver's rear, a little on the other wheels, but not much.

    Funny thing is, after bleeding the rears I had some pedal, but when we went to the front, I lost ALL of my pedal after we bled a wheel. Would not pump up at all...

    After I had someone take the top off of the MC, I got my pedal back. Actually, I seemed to get a little more pedal with the cap off of the MC... Does this make any sense?? It happened each time bleeding the front wheels... No matter how much we bled them, I lost all pedal, until the top was taken off of the master. Could it be sucking air in somewheres??

    I also forgot to mention, I plumbed the rear brakes to the rear resevoir (closest to the pedal), and the front to the front resevoir. The guy that helped me seemed to think I should switch them around, would this make any difference?
     
  18. Jimm56
    Joined: Aug 27, 2010
    Posts: 170

    Jimm56
    Member

    ^^what he said. 1/4 is just too much volume. The master cylinder will only push so much volume, yours is likely designed for smaller lines.
     
  19. badshifter
    Joined: Apr 28, 2006
    Posts: 3,320

    badshifter
    Member

    Sigh.....wrong wrong wrong. And oh yeah. Wrong.

    Unless you have invented a way to compress liquid with a measly 1200 or so psi.....
     
  20. andywuc
    Joined: Jul 1, 2013
    Posts: 4

    andywuc
    Member
    from london

    The piston must return to the base of its bore or you will trap air.[​IMG]
     
  21. Shaun1162
    Joined: Feb 22, 2010
    Posts: 833

    Shaun1162
    Member

    Yep, it's returning all the way..
     
  22. Dreddybear
    Joined: Mar 31, 2007
    Posts: 5,996

    Dreddybear
    Member

  23. Dreddybear
    Joined: Mar 31, 2007
    Posts: 5,996

    Dreddybear
    Member

    I'm in.

    I don't want to start anything but folks come here for answers and advice. So, Seriously, pressure is pressure. The line size has nothing to do with it. The only thing that the line size will change is the velocity of the fluid moving from one cylinder to another. The piston size will affect the EDIT:velocity too. In this application the difference between 1/4" and 3/16" is nothing. This is why my Model A with 40 ford brakes, a 1" bore master, and 3/16" lines stops fine.
     
    Last edited: Jul 2, 2013
  24. borderboy1971
    Joined: Oct 20, 2008
    Posts: 743

    borderboy1971
    Member
    from Canada

    I might as well through in my suggestion too. Jack the car up and readjust the brakes again. I have had situations in the past where, the shoes take a bit to center in the drums, and take a couple times of adjustment to get them correct, Then bleed them again. To adjust them correctly, there should be a very slight drag when spinning the wheel that you are adjusting (not even a drag really, more of just a dragging noise), and remember if they have individual adjusters for each shoe like early Ford brakes (others as well) that you need to adjust both shoes separately.

    I know it's been stated, but make sure you have a very small amount of free play when the brake pedal is released.... This actually causes a hard pedal buildup, as the fluid can't return to the Master cylinder properly, and the next time you apply the brakes you are "jamming" more fluid into the lines and cylinders, and the cycle repeats.
     
  25. willys1
    Joined: Oct 31, 2012
    Posts: 1,021

    willys1
    Member
    from South Ga

    ^^^he's right ^^^ line size is volume not pressure
     
  26. MBog
    Joined: May 2, 2006
    Posts: 552

    MBog
    Member

    Just a thought... Two things Nobody has asked if the master was bench bled, and secondly,are the bleeders all at the top? In other words maybe the backing plates are crooked and the cylinders are trapping air cuz the bleeder is not the highest point...
     
  27. Shaun1162
    Joined: Feb 22, 2010
    Posts: 833

    Shaun1162
    Member

    Thanks again guys for the advice

    I re-adjusted the front and rear brakes again yesterday- the front brakes did need a little adjusting, but it didn't help my pedal at all... I've rechecked the push rod, and it does return all the way

    Yes, it was bench bled. As far as I know none of the backing plates are bent/crooked, but I will be sure to look into that today...

    What I don't understand is why I lose ALL of my brakes when the front ones are bled- and then I regain pedal when the master cylinder top is taken off?? I've never heard of this happening before....
     
  28. LesIsMore
    Joined: Apr 8, 2008
    Posts: 449

    LesIsMore
    Member
    from Ohio

  29. Bigchuck
    Joined: Oct 23, 2007
    Posts: 1,141

    Bigchuck
    Member
    from Austin, TX

    Two things come to mind. first, where did the mc come from? Is it new or, a re-man? Imported crap or, made by a known good mfg? The part about it woking better with the lid off the mc could be that the lid is not venting. It should not be 100% sealed as you need atmospheric pressure to allow th mc to pull fluid from the reservoir into the bore. If all your fittings/lines are tight and there are no leaks, the problem has to lie with themaster cylinder.
     
  30. Dan Timberlake
    Joined: Apr 28, 2010
    Posts: 1,307

    Dan Timberlake
    Member

    "What I don't understand is why I lose ALL of my brakes when the front ones are bled- and then I regain pedal when the master cylinder top is taken off?? "

    Does the cover gasket have "accordions" built in?
    http://i.ebayimg.com/t/Master-Cylinder-Cap-Gasket-1967-1968-1969-1970-1971-1972-Mustang-Drum-Brakes-/00/s/MTA2M1g5ODA=/$(KGrHqJHJEEE-njyti9OBPs8nEF+Zg~~60_35.JPG
     

Share This Page

Register now to get rid of these ads!

Archive

Copyright © 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.