Strange 2012 Brake Action Related Noise

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by howardc64, May 28, 2019.

  1. howardc64

    howardc64 Member

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    2012 Prius II 115k miles. No error lights on dash, not yet scanned with Techstream.

    Makes this fair loud sound coming from the driver side of the engine bay whenever foot is completely off the brake. Sound goes away when pressing brake. Particularly noticeable coming to a stop in a garage where the noise echos.

    Following video is backing the car out 3-4 feet and going forward 3-4 feet. The sound appears when going forward whenever the foot is off the brake (at 10s and 13s mark of the video). My son comments the tone of the sound is like Apple Mac boot sound.

    Also seems like the sound starts after the car is warmed up (not sure, don't have enough stats yet as this is a friend's daughter's car I just got hold of to do oil change)

    Clearly brake action related. I believe the ABS and actuator/pump/accumulator are all between the inverter and the firewall? and probably source of the sound? Anyone has any ideas?



    Brake fluid might be a tad off but not much.

    IMG_0336.jpg
     
    #1 howardc64, May 28, 2019
    Last edited: May 28, 2019
  2. bisco

    bisco cookie crumbler

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    that's the vpns (vehicle proximity notification system)

    it is a pedestrian warning. toyota began installing them on the 2012 model year.

    it should be on in forward and reverse, anytime the car is moving between 0 and 15 mph. braking should not affect it unless you stop.

    most of the time, you can't hear it from inside the car. (and often outside)

    it reflects off garage walls nicely
     
    #2 bisco, May 28, 2019
    Last edited: May 28, 2019
  3. Grit

    Grit Senior Member

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    Brake fluid is well below minimum level, not a tad
     
    #3 Grit, May 28, 2019
  4. Mendel Leisk

    Mendel Leisk Senior Member

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    No, min level is down by that lower seam. Take another look at yours to verify. It is hard to see.
     
    #4 Mendel Leisk, May 28, 2019
  5. howardc64

    howardc64 Member

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    Cool thx! No worries for me then. I have a 2011 Prius and doesn't have this thus was alarmed. Have a 13 Tesla thats even quieter, I guess VPNS not mandatory.

    Looked up 2012 owner's manual and it shows the min line is below the reservoir seam so the pictured level is in between and should be fine? This picture was taken with the car off. Read in another thread that level rises when car is on. Owners manual doesn't seem mention anything about car on or pumping the brakes prior to checking the level.

    Screen Shot 2019-05-28 at 11.45.39 AM.png
     
    #5 howardc64, May 28, 2019
    Last edited: May 28, 2019
    Mendel Leisk likes this.
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    Also, if the car's sat overnight, and you pop the hood by going in on the passenger side and reaching across (leaving driver's door closed), you'll the usually see the reservoir level a good 1/2" higher. Then open the driver's door and you'll see the level drop, as the pumps are whirring.
     
    #6 Mendel Leisk, May 28, 2019
  7. bisco

    bisco cookie crumbler

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    all ev's are required by law to have vpns in the near future. for now, some have started complying early.

    there are threads here on how to defeat it for those not wanting the 'early option'.
     
    #7 bisco, May 28, 2019
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