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Technical Brake question!

Discussion in 'Traditional Hot Rods' started by DougMac, Oct 31, 2019.

  1. DougMac
    Joined: Nov 1, 2018
    Posts: 48

    DougMac

    My dad built a 1933 Dodge Hiboy 35 years ago. I recently bought the car back, but the brakes are acting up. Long story longer..... the car is drivable, but it has an incredibly hard brake pedal and breaking requires a ton of muscle. The last guy to own the car attempted to work on them without much success. The brake pedal is factory and remains like it did when we owned it and braking was easy. It has a single MC with a 3 bolt flange attaching it to the frame under the driver floorboard. From what I can tell, the brake ratio remains the same as before, but the bar running from the pivot point into the MC is adjustable. Drums on the rear, discs on the front. Fluid was bled, pads checked and even sanded. I did find that there are no check valves and no proportionate valve! You would think the back drums would lock up without the PV, but do not. The past owner bought the exact MC and replaced it, but no luck. I adjusted the rod running from the privet point into the MC to see if I could get more “stroke” into the cylinder, but the pedal has not changed. Anyone have any ideas before I start smoking crack?


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  2. DougMac
    Joined: Nov 1, 2018
    Posts: 48

    DougMac

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  3. DougMac
    Joined: Nov 1, 2018
    Posts: 48

    DougMac

    [​IMG]
    Here is the MC it has used before with success, but recently been replaced with again.


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  4. BJR
    Joined: Mar 11, 2005
    Posts: 9,814

    BJR
    Member

    Have you checked to see if you have a frozen wheel cylinder or caliper? Also if the brake hoses are old they go bad.
     

  5. Any idea of the bore size? May not move enough fluid,or build enough pressure.
     
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  6. DougMac
    Joined: Nov 1, 2018
    Posts: 48

    DougMac

    I thought about bore size as well. It’s 1 1/16 on these......which is bigger than I would want, but to get the 3 hole flange it’s what I’m stuck with. What Is confusing me is that it was the same model 1 1/16 bore before when the brakes worked well. They replaced the old MC with one exactly like it. In order to change the MC to a diffrent dual reservoir style, I would almost have to pull the body from the frame and make some serious modifications. I’m stumped.


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  7. DougMac
    Joined: Nov 1, 2018
    Posts: 48

    DougMac

    I have the car on jack stands. I’ve spun every wheel and applied brake and all seem to be working well..... it just takes a lot of muscle to get the car to brake when it’s under load in driving conditions or at a red light. Very firm brake pedal...... which made me think pedal ratio had been changed.... but it hasn’t been changed since they were operating well from before.


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  8. I'd look to see if the pads and shoes are glazed up. It may just need new shoes/pads and rotors and drums cut. Most cars here complain of NO brake pedal at all. Does it get worse as the car runs for a number of miles, as in the brakes lock themselves up?
     
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  9. alchemy
    Joined: Sep 27, 2002
    Posts: 20,405

    alchemy
    Member

    That bracket looks like a 40's to 50's Ford pickup truck pedal and master cylinder mount. Also looks like the pedal was modified to change the ratio. Don't know why, unless the top half of the pedal was also changed and they were trying to correct the ratio. It's usually thought that 6 to 1 is best for a manual brake pedal ratio.

    I can't diagnose your problem, but if you want to change that three-bolt master to a common two-bolt master (with a dual chamber), there are common adapters to do so. They are basically a half-inch thick plate that had three countersunk holes for bolting to the bracket, and two tapped holes that you screw the new master to it with. Many hot rod vendors that deal with old Fords carry them.
     
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  10. DougMac
    Joined: Nov 1, 2018
    Posts: 48

    DougMac

    Awesome! I had no idea on the adapter. I have a brand new dual MC (mustang) that might just be the solution. I really appreciate the advice!


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  11. How old are the rubber hoses? They might be restricting flow.If the rear was bad you could be using front brakes only.
     
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  12. BBAA95DD-50F4-4447-A0D8-52AC2569B9CB.jpeg

    1-1/16” bore size
     
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  13. Doublepumper
    Joined: Jun 26, 2016
    Posts: 1,534

    Doublepumper
    Member
    from WA-OR, USA

    I'd be very suspect of the hoses. Just because the brakes work while spinning the wheels on jack stands doesn't mean the hoses aren't collapsing when under load of stopping the car in driving conditions.
     
  14. Someone has screwed around with the pedal ratio before.

    CC854876-8704-41FB-AA47-D32863E02FC4.jpeg
    Use of That lower hole that’s been ground off would decrease foot travel, increase stroke length, and increase the amount of foot effort.

    You really need to measure the psi development at the wheels. Go from there. Last guy had 1200 psi and couldn’t stop because of insufficient friction materials.
     
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  15. DougMac
    Joined: Nov 1, 2018
    Posts: 48

    DougMac

    I moved the positioning to that lower setting and increased the adjustable (threaded) rod that moves into the MC hoping to get more stroke. I actually unthreaded it’s to much and bent the crap out of it the first time I hit the brake pedal. I’ve got a new rod headed this way and I’ll experiment from there. Any idea how far that rod should move if it was getting full stroke?


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  16. It’s usually an 1” stroke but some aremore
    A problematic hard brake pedal that does move wont be a full stroke issue.

    It will be a mechanical advantage hydraulic solution, or a friction material issue not stopping the car. The quickest fastest easiest way to figure that out is the spend $50 on a test kit that screws in a bleeder holes and tells you to psi at the wheels. It got shitty pressure Dan will be a bore size ratio thing, If it’s got good pressure and still won’t stop it’s a friction problem with the pads shoes or braking surfaces.

    It’s cut and dry. Black and white. No guessing no tail Chasing Very little frustration
     
  17. SASROD
    Joined: Feb 7, 2007
    Posts: 149

    SASROD
    Member


    How much pressure should you have at the bleeders, for a typical system? Say for drum/drum or drum/disc systems.
     
  18. oj
    Joined: Jul 27, 2008
    Posts: 6,454

    oj
    Member

    You see that little dribble coming from the center of the boot? I'll bet there's crud inside the boot that won't let you push squarely on the piston (thats the binding part), peel the boot back and they'll probably be a dribble of brake fluid inside, some nasty stuff, barnacles and shit you'll have to muck out. Once you get the piston freed up you'll be good to go. There's a snap ring inside the boot, remove it and push from the backside with a rod and all the goo will come out, there'll be a spring, special washers, piston and stuff. Keep the right order for reassemble. take carb cleaner and muck the thing out and put it back together, doubt you need rebuild kit.
    Drum brakes take about 400psi.
     
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  19. I agree with the master being crapped up. Parts stores used to carry those EIS kits in just about any master size, no clue if they still do. I'm sure you can find a kit for it.
     
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  20. jimvette59
    Joined: Apr 28, 2008
    Posts: 1,107

    jimvette59
    Member

    You should be using a M/C for disks and drum. That old ford M/c is not doing it. JMHO
     
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  21. inthweedz
    Joined: Mar 29, 2011
    Posts: 580

    inthweedz
    Member

    I have just overhauled the left rear wheel cylinder on my car. I noticed under hard braking, that the RR would chirp the tire, but not the LR.
    I stripped it down, one piston was totally seized, and one was only just moving..
    The cylinder had previously been sleeved, cleaned it up, lubed with rubber grease and fitted new cups, beld it up, and works like it should now..
    In your case I would start with the rear cylinders, if they are double acting, or two per wheel, you could find only half are working to give you the braking effect while on the axle stands.
    The real fix would be to remove all cylinders and hoses, and check everything..
    Any car that sits more than getting used is prone to brake cylinder problems, the brake fluid absorbes moisture, and with the brake dust will slowly gum up the cylinder pistons, seizing/rusting them till in the end they are solid.
     
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  22. Yes.. how did I miss that? Completely not good for the application.
     
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  23. DougMac
    Joined: Nov 1, 2018
    Posts: 48

    DougMac

    After looking at the pedal ratio, which is correct, I’m finding that the only time I’m getting any movement from the rod into the MC is when I bleed the brakes. Otherwise, I’m really not getting any “stroke” at all in the MC. I pulled the MC and it looks brand new. It has a 3 way block on the back with 2 lines going to the front disc, 1 going to the rear drums. I’m going to work my way back to the drums and replace the rubber hosing (if not all the brake lines as it’s not that much. I will definitely check the drum cylinders and make sure they are all operating.....at this point, I have zero stroke in the MC if the line is bled. Somthing isn’t allowing the fluid to move as it’s intended.


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  24. I’m curious why that master will activate brakes any different than one for a disc drum system? It doesn’t know what it’s moving fluid too. Other than a possible residual valve mismatch, which is not causing this problem. The 1 1/16 bore may not be generating enough pressure causing a hard pedal without stopping well but as 31 Vicky has tried to say without testing anything you are guessing. It’s not rocket science.


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  25. Not rocket science but you got to be smarter than the brake fluid.

    Some obscure master cylinders have dual bore sizes .
     
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  26. The fluid moves just fine ,,, you said so when you open the bleeders you get stroke and fluid. It that on all 4?
    Perhaps the cylinders and calipers are mechanically bound up somehow. Did you look for movement in there ? Are they all 4 corroded?
    What’s the line pressure?

    CDD95C2D-B330-4BE7-8611-2CB27F39104E.png
     
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  27. Some but not many.


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  28. DougMac
    Joined: Nov 1, 2018
    Posts: 48

    DougMac

    I get it with the gauges. But,there is absolutely zero stroke inside the MC and very little pedal movement with the hard break. I already know it doesn’t have the correct pressure, because how could it? I’m going to bleed the back drums tonight and pull the hubs and see if any cylinders are bound. Thanks for the advice!


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  29. So you haven’t measured anything but know it doesn’t have the correct pressure, maybe have a read on basic hydraulics, if everything is seized the master can’t move. You said it moves when the bleeders are open, correct? If that’s the case then calipers and wheel cylinders are not moving. Have you watched to see if they are?


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