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Brakes "fart" when I press lightly

Discussion in 'Gen 3 Prius Technical Discussion' started by corystal, Aug 17, 2019.

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  1. corystal

    corystal Junior Member

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    There's a similar thread over in Gen2 but all the replies refer to "creaks"... but this is a definite "fart" sound... not like a ripper, but a tight little fart you tried to sneak out. If you've heard it, you know :D

    It started this morning, and I am at a higher elevation than where I live and it's somewhat hot... but it's not any higher or hotter than the car has ever been, so I wouldn't guess that is a factor.

    Every time I press the brake pedal gently (as in, the car doesn't actually even slow down) the noise occurs from under the dash, where the pedals are. If I really apply the brakes hard and quickly it doesn't happen, or there might just be a bit of a squeak.

    Another clue is that a little after I turned off the car and the brake system made it's "psst-cluck" noise.. that was a fart too!
     
    #1 corystal, Aug 17, 2019
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  2. bisco

    bisco cookie crumbler

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    there have been descriptions such as hacking and honking as well. there is a new extended warranty out, 10years or 150k if it fails
     
    #2 bisco, Aug 17, 2019
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  3. CR94

    CR94 Senior Member

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    Mine went through a period of grunting when I released the pedal. Chapman has a theory involving bubbles in the fluid.
     
    #3 CR94, Aug 18, 2019
  4. corystal

    corystal Junior Member

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    Thanks.. I'll look into it
     
    #4 corystal, Aug 19, 2019
  5. corystal

    corystal Junior Member

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    [UPDATE] Driving back today, it stopped.. so maybe elevation is a factor...??? 6800ft -> 20ft above sea level
     
    #5 corystal, Aug 19, 2019
  6. corystal

    corystal Junior Member

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    "Chapman"?

    I did check the brake fluid level which was fine. Perhaps a bleed is in order if it comes back.
     
    #6 corystal, Aug 19, 2019
  7. ChapmanF

    ChapmanF Senior Member

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    Beyond any "theory" I might have personally, there was also a service bulletin, T-SB-0363-10, for the earlier Gen 3s, about a firmware update to reduce the fart noises. It gives the firmware revisions that included the fix (F152647108 for cars with 15" wheels, F152647128 for 17").

    It's easy enough to check with Techstream whether you have the right version or later. If you have a 2012, maybe you already do (in which case, we'd be back to "theorizing" about what to do next). But if you don't have the fixed firmware, there's an answer for that.
     
    #7 ChapmanF, Aug 19, 2019
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