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Brake light on still!!!After 3/4 ton conversion

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 87superblaze, Apr 18, 2002.

  1. 87superblaze

    87superblaze 1/2 ton status

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    Here's the story. I recently converted to D44 front and 14BFF rear. I replaced the calipers brake lines and wheel cylinders in the front and rear. I bled the bloody piss out of the lines, gravity feed...... and the brake light is still on! It was not on before the switch to 3/4 ton.

    What could be wrong? What should I look for? I just rebuilt the engine too at the same time of the axle swap. A couple of years ago I noticed the brake pedal surging but it stopped in a few weeks so I ignored it.

    Do I need the master cylinder or booster from the donor truck? I don't know what year it was but I think it was a '74.

    Please, I would be forever thankful for any help with this problem.
     
  2. BorregoK5

    BorregoK5 1/2 ton status

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    This is a shot in the dark, so someone speak up if they think its off base. The rear drums have return springs and the capacity needed to activate the brakes would be increased with a larger drum/slave cylender (or if the rear is adjusted too loose). Since the light is triggered by the proportionaing valve, maybe it thinks the pressure difference is a problem when its really just a result of a changed condition. Stock proportioning valves aren't adjustable.
     
  3. 87superblaze

    87superblaze 1/2 ton status

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    My rear brake pads might be adjusted too loose. Could this be the cause of my problem?

    I had to rig up some sort of catch on the adjusting bolt/nut so it will hold the slot on the pad. Any thoughts?
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    I've never actually taken the cap off and looked, but have you tried pushing in the nub on the end of the prop valve? http://www.dorianyeager.com/combovalve.html

    I stole that from Grim BTW : )

    Aside from that, it could be that your master cylinder is just shot. Are you getting a firm pedal or is it spongy? I'm pretty sure the rear drum shoes need to be adjusted right to prevent pressure problems as well.
     
  5. BorregoK5

    BorregoK5 1/2 ton status

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    What happened to prevent the adjusting nuts normal opperation?? Did something break?
     
  6. 87superblaze

    87superblaze 1/2 ton status

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    I have tried the button on the prop valve. The pedal feels normal but the truck doesn't stop as fast as it should. If I stomp on the brakes teh tires don't come close to locking up. It almost feels like there is air in the lines but there can't be when the flow is good out the bleeders and the fact I went through two containers of brake fluid.
     
  7. 87superblaze

    87superblaze 1/2 ton status

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    Yes. One of the forks broke off when I tried to bend it back. I wasn't able to run to the parts store for a new one. All I did was very cheesy but I put a small bolt through the hole with 2 large washers to prevent the bolt from moving side-to-side. I will fix it some day. I was a little too anxious to try out the new axles!
     
  8. BorregoK5

    BorregoK5 1/2 ton status

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    Anxious and ambitious! LOL, well, your symptoms sound more like a vacuum booster problem than fluid problem. You should be able to lock the front brakes or meet the floor otherwise. I had a bunch of issues with my brakes when I first got the truck, master cyl and booster(s) related. I finally gave up and went hydrabooster... a good permanent fix with excellent braking! You've got me on this one!
     
  9. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Check if your E-brake is on and pressure bleed your brakes. Gravity bleeding isn't enough.
     

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