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Lower Brake Pedal Arm Return Spring?

Discussion in 'Early CJ5 and CJ6 Tech' started by truckee4x4, Nov 21, 2021.

  1. Nov 21, 2021
    truckee4x4

    truckee4x4 Grant Kaye 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Truckee CA
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    View attachment 74502 Is there supposed to be a return spring on the lower part of the brake pedal arm that goes to the brake and clutch cross shaft? I can’t quite figure out how else I can keep the plunger in the master cylinder.

    There is a hole on the pedal arm… I would just have to add a hole on the master cylinder bracket to span between the two.

    UNADJUSTEDNONRAW_thumb_8464.jpg
     
    Last edited: Nov 22, 2021
  2. Nov 21, 2021
    Oldpappy

    Oldpappy A.C. Fults - Curmudgeon at large 2021 Sponsor

    East Tennessee
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    You are thinking backwards on this one.

    One end of the spring hooks to the pedal arm and the other end hooks to the crossmember. If you have a correct length on the plunger rod it won't fall out. The pedal pushes the plunger into the master cylinder, the spring pulls it back out when you let off the brake.

    If you have so much slop in the setup that you fear the rod will fall out you probably have the wrong plunger rod.

    You also need to properly lock those cotter pins so something doesn't fall apart.
     
  3. Nov 21, 2021
    Jw60

    Jw60 WRPD855 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    floorboard usually keeps it all together maybe use some coat hanger or string to keep it from flopping out. Also a washer between the cotter pin and the rod will keep it from wearing and rubbing the cotter pin. Also looks like it will be easier to service with the eye down once the body is on.
     
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  4. Nov 21, 2021
    Oldpappy

    Oldpappy A.C. Fults - Curmudgeon at large 2021 Sponsor

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    Yeah, I wasn't thinking about not having the body on. JW60 is right. Without the floorboard to stop the pedal it will pop out the rod.
     
  5. Nov 22, 2021
    CHUGALUG

    CHUGALUG Member

    Silverton, OR
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    Also doesn't that boot slip down over the end of the MC?
     
  6. Nov 22, 2021
    truckee4x4

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    Boy you guys are sharp!

    Yes the boot slips over, yes I know I need to finish the cotter pins - but I'm not going to do these things until I know the rod is the right length, and about 27 other things on a long to-do list before I am done. I just pulled the body back off the frame for paint prep so I'm going back over all the systems slowly and methodically.

    I guessed at the plunger rod length to give the lower pedal arm the same "cant" as the clutch pedal arm.

    I'm aware that the brake pedal will be held "down" (and the piston in the cylinder) by the floor pan, but it seems wrong to me to rely on this. Why not add a short spring along this yellow line to keep the piston in?

    IMG_0613.jpg
     
    Last edited: Nov 22, 2021
  7. Nov 22, 2021
    45es

    45es Member 2021 Sponsor 2020 Sponsor

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    First, the piston is held within the master cylinder by a retainer spring clip, not the brake petal push rod. Secondly, adding a spring to pull the brake petal into the master cylinder eliminates the free play adjustment called for in your manual.
     
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  8. Nov 22, 2021
    truckee4x4

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    Does the retainer spring clip apply to the dual reservoir master cylinder that I have modified onto my jeep? If so where does it go?
     
  9. Nov 22, 2021
    45es

    45es Member 2021 Sponsor 2020 Sponsor

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    Yes. Within the master cylinder, just in from the end where the pushrod enters, you should see a groove machined around the bore. The clip is retained in the bore at the groove.
     
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  10. Nov 22, 2021
    truckee4x4

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    Fantastic, I knew I was missing some thing obvious, thank you!
     
  11. Nov 22, 2021
    Michael Wedin

    Michael Wedin Member

    Sweetwater, TX
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    Remember the pedal/rod will be kept in/down with the floorboard once the body is back on. No need for the additional spring.
     
  12. Nov 22, 2021
    truckee4x4

    truckee4x4 Grant Kaye 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    Just so we're on the same page - here's a pic of the cylinder bore. The rod that came with the kit is smaller than the bore and is loose within it - right? Hey cylinder bore is 0.48, and the bulbous end of the pushrod is 0.38.

    UNADJUSTEDNONRAW_thumb_846e.jpg UNADJUSTEDNONRAW_thumb_846f.jpg
     
    Last edited: Nov 22, 2021
  13. Nov 22, 2021
    45es

    45es Member 2021 Sponsor 2020 Sponsor

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    Yes, and of course, you see the snap ring within the bore.
     
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  14. Nov 22, 2021
    EFranzen

    EFranzen New Member

    Queen Creek AZ
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    Here's a view of the original style rod clip and keeper.
    upload_2021-11-22_19-49-17.png
     
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  15. Nov 23, 2021
    Fireball

    Fireball Well-Known Member 2022 Sponsor 2021 Sponsor 2020 Sponsor

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    As others have noted, the pedal return spring needs to be pulling the pedal away from the master cylinder not towards it. There needs to be some free play in the pedal to ensure the master cylinder returns completely and opens up the compensating port so the brakes don't drag. The pedal can only go so far back once the floorboards are in.

    You can see the return spring hooked to a hole in the hat channel on my '69:
    [​IMG]
     
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  16. Nov 23, 2021
    Twin2

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    just my 2 cents
    stock master cylinder . push rod is retained to piston ( as pictured above )
    problem solved
     
  17. Nov 23, 2021
    truckee4x4

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    Thanks guys this is making much more sense.
     
  18. Feb 20, 2022
    truckee4x4

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    What is the procedure to determine the correct length of the pushrod? I suspect mine is too long and not letting the piston return all the way as I am not getting fluid to pull out of the forward tank. I had the brakes bled properly before the body was on, then I had to make some changes after it went on.
     
    Last edited: Feb 20, 2022
  19. Feb 20, 2022
    Jw60

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    The general rule of thumb I've always seen was 1" free travel at the pedal. That keeps any fluid expansion from locking up the system.
     
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