Clunking sound when braking

Discussion in 'Gen III 2010+ Prius Main Forum' started by ES44AC, Sep 6, 2012.

  1. ES44AC

    ES44AC C.A.U.S

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    I am noticing a sort of clunk or knocking noise from under the hood when I hit the brakes. I thought it might be the pads, but it comes from under the hood .It only makes the sound on the first touch of the brake, once you have your foot on the pedal it stops the noise. It does this every time on the first application of the pedal.

    Is this sound normal? I don't recall hearing it when I test drove the car, maybe it's been there all along and I am just now making note of it.

    Thanks to all :D
     
  2. spiderman

    spiderman wretched

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    According to my dealership service department,,, yes it is normal.

    I too thought it was the pads slipping around but they say it is the brake actuator doing its thing (if in fact it is the same sound we are hearing). Considering the prius really just simulates braking (while regeneration occurs) I gave them the benefit of the doubt. ;)
     
  3. The Critic

    The Critic Resident Critic

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    It's rust build-up. Usually its accompanied by some noise as well. If you've noticed, it almost always goes away after the first or second brake application.
     
  4. jdcollins5

    jdcollins5 Senior Member

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    The next time this happens, when slowing for the next stop put the car in neutral. This will disconnect the HV battery which will disable the regen braking and force the friction brakes. Do this a couple of times and this will help remove any rust on the rotors and help keep the calipers from sticking.
     
    mad-dog-one likes this.
  5. mad-dog-one

    mad-dog-one Prius Enthusiast

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    Follow this method and note whether the clunking sound is eliminated. This will isolate any problem with mechanical braking by eliminating regen braking.
     
  6. ES44AC

    ES44AC C.A.U.S

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    Hi,

    No it doesn't go away ever. I can sit in my garage and depress the brake and each time I do it I hear that noise.

    I will try what the others suggest but I have my doubts about it working.

    Thanks