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Brakes

Discussion in 'Brakes' started by Omar, Jun 15, 2019.

  1. Omar

    Omar Junior Member

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    Location:
    Texas
    First Name:
    Omar
    Truck Year:
    1981
    Truck Model:
    C10
    Engine Size:
    350
    Hello folks...
    I just bought a 1981 c10 needs some work, so it's a work In progress. My question is the rear brakes were bad so I went ahead and replaced pads drums,springs and cylinders. Once I had everything installed and started to bleed them using the buddy system. My buddy would pump the the brakes and hold but when I opened the bleeder valve I got nothing??? This went on for several attempts when I finally just had him mash the pedal, and at that point I got fluid. Once i was done we put the wheels back on and did a road test all was fine when i decided to mash my brakes as if it was an emergency, the truck stopped but when I released the pedal my rear brakes stayed locked up? I made it back home but my rear brakes were just a little hot...so my question is what should my next move be to check? Could it be my combination valve sticking? Any help would be appreciated...
     
  2. 78C10BigTen

    78C10BigTen Full Access Member

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    First Name:
    ted
    Truck Year:
    1978
    Truck Model:
    C10 BIG TEN
    Engine Size:
    350
    My first thought is a bad proportioning valve but im not good with brakes so... im sure more experienced people can help here. Be patient....
     
  3. 78C10BigTen

    78C10BigTen Full Access Member

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    Engine Size:
    350
    Also just a thought that has nothing to do with the fluid but check to make sure your E brake hasnt been engaged in anyway somehow. Starting simple...
     
  4. Old77

    Old77 Super Moderator Staff Member

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    Location:
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    First Name:
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    Truck Year:
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    Truck Model:
    C10 longbed/R3500 Dually
    Engine Size:
    350/454
    Not sure why this was posted in the Introduction section but I’ve moved it to the proper area for you
     
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  5. Omar

    Omar Junior Member

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    First Name:
    Omar
    Truck Year:
    1981
    Truck Model:
    C10
    Engine Size:
    350
    Thank you...
     
  6. 75gmck25

    75gmck25 Full Access Member

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    Truck Year:
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    Truck Model:
    K25
    Engine Size:
    5.7
    IIRC, you have to manually flip the switch on the proportioning valve when you are bleeding the brakes, so that it provides equal pressure to both front and back systems. The valve should be located on the front driver's side of the truck, up under the left side frame rail or radiator support. You can follow the brake lines down to it.

    In failure mode the proportioning valve is designed to switch internally and shift pressure to whichever brake system is still good, so it sends all pressure to the brakes that still hold. This means it may not pressurize the brake you are bleeding (since the valve is open) and you will have trouble getting it to bleed properly.

    Bruce
     
  7. bucket

    bucket Super Moderator Staff Member

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    Truck Year:
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    Truck Model:
    K5 thru K30
    Engine Size:
    350-454
    I've never had to mess with the prop valve on these trucks when bleeding the brakes. While it may be the technically correct way, it's never been an issue.

    Is it for sure both rear brakes hanging up? It could be the rear brake hose is collapsed internally and retaining pressure in the wheel cylinders.
     
    HotRodPC, 4WDKC and CSFJ like this.
  8. rohuie

    rohuie Full Access Member

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    Location:
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    Truck Year:
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    Truck Model:
    R10 Silverado SWB, K5 Silverado Blazer
    Engine Size:
    350 TBI, LS Swap 6.0
    Unless the prop valve is bad, there is no need to reset the slider to the middle.
    I've had to replace one on my K5 as it had been sitting for many years.
    Also are you getting a brake light on your dash even if the e-brake is off?
    There is a sensor on the prop valve that will trigger the light in the dash if it has gone bad. Also if fluid is only going to front or rear.
     
  9. 4WDKC

    4WDKC Full Access Member

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    Truck Year:
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    Truck Model:
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    Engine Size:
    350
    sounds like the flexible line to the rear brakes collapsed and is restricting fluid from returning to the master cylinder. Lift the truck loosen the lines from each wheel to the flexible line on the rear axle then close it. Should be enough pressure release to turn the rear wheels. Replacement lines are inexpensive.
     
  10. HotRodPC

    HotRodPC Administrator Staff Member

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    Truck Year:
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    Truck Model:
    Silverado K10 to K20 Conversion
    Engine Size:
    6.2 to Gas???
    My vote is also for a collapser rubber hose just before the T over the axle pumpkin. Can't cost that much and it's time to replace it anyway so it's not a waste to give it a try.
     
  11. rohuie

    rohuie Full Access Member

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    Truck Year:
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    Truck Model:
    R10 Silverado SWB, K5 Silverado Blazer
    Engine Size:
    350 TBI, LS Swap 6.0
    Right it's $10 - 15 at most local part stores.
     
  12. Charlie

    Charlie Full Access Member

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    First Name:
    Don
    Truck Year:
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    Truck Model:
    Cheyenne 10 LWB
    Engine Size:
    350/TH350/AC/4 BBL Quadrajet
    :welcome:
     

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