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"Grabby" brakes = cocked piston

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by DieselSub, Jan 15, 2006.

  1. DieselSub

    DieselSub Registered Member

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    Over the last week my truck has started giving a "popping" noise sometimes when starting up from a dead stop. I then noticed that at the very end of a stop (going from 1/4 mph to zero) the brakes would grab with a sudden stop sometimes. Those same times I could release the brakes and the truck wouldn't move forward - I have to give it a little gas to brake it free.

    So I pulled the calipers and sure enough one sides brakes were unevenly worn and the caliper was cocked. I got a new caliper but would like to know what caused this. Has this happened to anyone else?

    I noticed that the cocked calipers inner brake pad was missing the retaining clip that goes inside the piston. Could this have contributed? Also, the caliper that failed was a rebuilt unit from Pep-Boys. Maybe the rebuilt one's bore was not honed? (I forgot to check this before swapping it as a core)

    I'm already fixing it (got a new caliper), but am curious why this happened...

    Thanks,

    Mike
     
  2. imiceman44

    imiceman44 1 ton status

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    That happens from running hot rotors in water, that warpes them, starts a wobble which wears out the leading edge of the pads, which puts pressure on the piston and wedges it.
    Turning those rotors makes it even worse.
    Only turn rotors that are grooved or scrathed, or have a lip.
    Warped rotors are trash.
     
  3. DieselSub

    DieselSub Registered Member

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    Rtfm

    My Factory Service Manual cleared things up. When I pulled my brakes apart two things were wrong:

    The caliper retaining pins were badly corroded. And the FSM says any corrosion at all is grounds for replacement and *do not* try to polish them back up. Off to Kragens for $8 a piece pins (does someone have a cheaper source?)

    The backing plate clearance was wrong. There is supposed to be .005-.012" of clearance at the four places the backing plate "touches" the caliper. One of those places was tight on my truck. The FSM says to file the backing plate to resolve the clearance issue.

    Thanks again for everyone's help.
     

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