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How does the drum brake self adjuster work?

Discussion in '1973-1991 K5 | Suburban | Truck' started by fredekr, May 21, 2003.

  1. fredekr

    fredekr Registered Member

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    I took apart my rear brakes last weekend because of the following symptoms:
    1. The right rear likes to lock up when the vehicle is cold.
    2. It pulls to right under heavy braking.

    Front pads and rotors were replaced very recently.

    Here's what I found:
    1. Left rear wheel cynlider seal were destroyed. Cobwebs in drum... maybe that one doesn't see much action?
    2. Small axle seal leak on right rear.
    3. Self adjuster on right rear contacts star wheel

    It's #3 that I am wondering about. On the left side the adjuster lever doesn't rest against the star wheel, on the right side it does. What should it be like?

    Here's a picture of the right side:
    [​IMG]

    Do I need to replace the adjuster or shoes or what? What's it supposed to be like?

    thanks,
    Kevin
     
  2. gumneck

    gumneck Registered Member

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    Kevin,
    On the right side, are all the springs fitting in the right holes like they should. If not that maybe why adjuster is resting on it. I can't remember if its supposed to be on it full time or not. I think it is. I've been working on my rearend & have replaced the axle seals so my rear tires are off. I'll check mine after work today and get back to you on what mine looks like in case no one replies before that.

    Also, you should have light friction b/n shoes and drum. You might put the drum back on and see if you can turn it hearing only light rubbing and it shouldn't be hard to turn the drum. If it is adjust the wheel so shoes kick out a little less.
    Tom
    1991 blzr getting new valvoline 80w90 in the rear tonight!
     
  3. 79Jimmy

    79Jimmy 1/2 ton status

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    Yes, that lever should be resting on the star wheel. This is how the rear brakes are kept in adjustment, when it works. /forums/images/graemlins/smirk.gif Every time you use your parking brake that lever is forced downward against the star wheel which is theaded left or right depending on which side of the truck it is on. As the lever comes down it catches on the wheel, unscrewing it and thus extending it which in turn pushes the brake shoes apart and against the drum. If the shoes are already adjusted properly against the drum the lever just skips over the star. Over the years the lever and star can wear out, become rounded, and cease to adjust properly. Hope that helps.

    James
     
  4. HarryH3

    HarryH3 1 ton status Author

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    Check to see if that spring just behind the lever is installed backwards on the side where the lever isn't touching the star wheel. On some drum brake setups that will have the spring pushing the lever away from the star wheel. /forums/images/graemlins/frown.gif

    The grabbiness is due to lube and/or brake fluid on the shoes. Fix the leaks, replace the shoes, and clean everything really well with brake cleaner. /forums/images/graemlins/eek.gif Then your back brakes should work just fine.
     
  5. fredekr

    fredekr Registered Member

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    Thanks to everyone for their replies!

    [ QUOTE ]
    Check to see if that spring just behind the lever is installed backwards on the side where the lever isn't touching the star wheel. On some drum brake setups that will have the spring pushing the lever away from the star wheel.

    [/ QUOTE ]

    Which spring: the tension spring that pulls the shoes together and runs parallel to the adjuster screw, or small the compression spring that pushes that adjuster away from the shoe? Or the hold down spring that the adjuster pivots on? I think all three are installed correctly but I'll double check and see what I can see.

    [ QUOTE ]
    The grabbiness is due to lube and/or brake fluid on the shoes.

    [/ QUOTE ]

    Yes, I know that's part or all of the pulling problem and will fix it as suggested ... once I finish some other projects /forums/images/graemlins/tongue.gif

    thanks!
    Kevin
     
  6. fredekr

    fredekr Registered Member

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    [ QUOTE ]
    Every time you use your parking brake that lever is forced downward against the star wheel which is theaded left or right depending on which side of the truck it is on.


    [/ QUOTE ]

    I thought I had read about them adjusting when applied in reverse, but this makes more sense...

    thanks,
    Kevin
     
  7. HarryH3

    HarryH3 1 ton status Author

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    [ QUOTE ]
    Which spring: the tension spring that pulls the shoes together and runs parallel to the adjuster screw, or small the compression spring that pushes that adjuster away from the shoe? Or the hold down spring that the adjuster pivots on?

    [/ QUOTE ]
    That biga$$ tension spring that pulls the shoes together. /forums/images/graemlins/cool.gif
     
  8. BrianDamage

    BrianDamage 1/2 ton status

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    [ QUOTE ]
    [ QUOTE ]
    Every time you use your parking brake that lever is forced downward against the star wheel which is theaded left or right depending on which side of the truck it is on.


    [/ QUOTE ]

    I thought I had read about them adjusting when applied in reverse, but this makes more sense...

    thanks,
    Kevin

    [/ QUOTE ]


    I don't know where he's getting that parking brake thing. That's the first time I've heard that one.

    quote from the Hayne's manuel:

    "....If the brake pedal goes to the floor, further adjustment is required. If the brake pedal is low, back the vehicle up, making repeated stops, to actuate the self-adjustors, which work only when the vehicle is in reverse. Test the brakes for proper operation before driving in traffic."
     
  9. 79Jimmy

    79Jimmy 1/2 ton status

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    I stand corrected. Thanks for the info /forums/images/graemlins/thumb.gif

    James
     

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