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Brake Issues With Disc/drum

Discussion in 'Early CJ5 and CJ6 Tech' started by JHot, Sep 22, 2022.

  1. Sep 22, 2022
    JHot

    JHot New Member

    Sacramento Ca.
    Joined:
    Aug 10, 2016
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    2
    Hello guys,
    I’m having issues with my brakes. I swapped a Dana 30 with disc brakes in my 52 cj5 still using my stock MC(under the floorboard) .
    After first everything was working fine but I’ve ran into an issue with my brake peddle becoming extremely squishy with zero pressure. I’ve followed focker’s thread on front disk brakes and added Wilwood 2lb residual pressure valve.
    Could I be signs of a bad master cylinder?

    Any recommendations on steps on fixing it would be great!
     
    Last edited: Sep 23, 2022
  2. Sep 22, 2022
    Stakebed

    Stakebed Member

    Lake Co....
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    Aug 2, 2022
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    A stock '52 CJ5 master cylinder being used with 70's disc brakes??
     
  3. Sep 22, 2022
    Jw60

    Jw60 Airbender and interrupter of the light guard. 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Sedalia MO.
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    I've got the same master cylinder with 4 wheel disk.
    To the OP did you only add the 2lb valve for the front? do you have a 10lb valve to the rear or are you just exercising the return springs on the rear?
    Otherwise check the brake light switch and flex hoses.
     
  4. Sep 23, 2022
    Fireball

    Fireball Well-Known Member 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Pullman, WA
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    It's also not clear the OP disassembled then removed the drum residual pressure valve from the original master cylinder.

    Parts 8 and 9 shaded in yellow:
    [​IMG]
    As I understand it, you need to remove those parts and then put a 10lb valve in the rear line for the drums and the 2lb valve in the front line for the disks.

    That said, I haven't done it. All my Jeeps have the dual master cylinder where the residual valves are under the fittings on the outside.
     
    Last edited: Sep 23, 2022
    Stakebed and melvinm like this.
  5. Sep 23, 2022
    JHot

    JHot New Member

    Sacramento Ca.
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    Aug 10, 2016
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    I only added a 2lb valve coming out of the master cylinder for the front disc brakes. I’m assuming messed up and need to add the 10lb for the rear and remove the check valve?

     
    Last edited: Sep 23, 2022
    Stakebed likes this.
  6. Sep 23, 2022
    Jw60

    Jw60 Airbender and interrupter of the light guard. 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Sedalia MO.
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    Yep, gotta pull the parts 8 and 9 as Fireball posted. This can be done in the vehicle by pulling the plunger out and pulling on the spring 9 is a weird hat pressed into the spring and 8 is a rubber disk which isn't critical to remove.
    Spring goes back in.

    Once the original valve is out you need to replace the valve after the lines seperate to front and rear circuits. Disk get 2lb and drum need the 10lb valve. This keeps the wheel cylinders and calipers "primed" to speak. Drums are heavier due to the springs on the shoes.

    Don't forget to bleed and top off brake fluid, you might use more than the reservoir holds getting the rears filled again.
     
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  7. Sep 23, 2022
    Keys5a

    Keys5a Sponsor

    Florida Keys
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    A squishy pedal is a sign of air in the system. Re-bleed the brakes. If this doesn’t fix it, its likely the master cylinder.
    -Donny
     
    Stakebed likes this.
  8. Sep 23, 2022
    duffer

    duffer Rodent Power

    Bozeman, MT
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    Yes, but as posted, lacking or improper retaining valves will do the same. Squishy until all the "slack" is taken up and, depending on the system, your pedal may be on the floor by then.
     
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  9. Sep 23, 2022
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    This.

    The other thing that could be happening is brake fluid boiling because the brakes are held on causing vapor in the system.
     
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