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Strange High Frequency Buzzing (or Hissing) Sound at Rear?

Discussion in 'Gen 3 Prius Technical Discussion' started by Qboy61, Jun 20, 2010.

  1. Qboy61

    Qboy61 New Member

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    This morning I went to my garage and there was a strange sound that sounded like air or water hissing. I tracked it to the underside of my 2010 Prius at the rear of the car. It sounded like it was comming from the battery section and it sounded like a relay or something buzzing. I'm not sure how long the car was making this noise but it continued for about 5 minutes (while I let the dog outside LOL). I was nervous that something was going wrong since the car was parked for over 7 hours. It sounded similar to the high frequency buzz of newer fuel pumps. I should have investigated it further (opening the rear hatch maybe, duh) before disturbing the car. I only bent down to listen under the car and identified the noise source as near the batteries at the back. I got in and started the car but nothing abnormal appeared. Main battery level was about where it was when I parked. I ran the car for 20 seconds and stopped it but now the sound was gone.

    Anyone have any ideas what this was?
     
    #1 Qboy61, Jun 20, 2010
  2. David Beale

    David Beale Senior Member

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    It's the valves in the vapour recovery system for the fuel system. Sometimes they don't seal properly and "vibrate" causing strange sounds. Pearl does the same thing from time to time. Not very common though. I've heard it twice in three years. The fuel expanding and contracting with temperature will cause the system to function. It happens more often with ethanol fuel, as there is a higher vapour pressure with it.
     
    #2 David Beale, Jun 21, 2010
  3. DTM255

    DTM255 Junior Member

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    The same exact thing happened to me last night (also letting my dog out and waiting in the garage). Hissing noise started while I was sitting in the garage. After a few minutes I started the car, checked battery level, and then turned it off. Now the noise is gone. It sounds more like a electric noise instead of the noise from valve. Can anyone confirm what this noise is?
     
    #3 DTM255, Nov 23, 2010
  4. David Beale

    David Beale Senior Member

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    There is also a vapour purge cycle that happens about 5 hours after you shut off the car. It uses an electric pump. This cycle purges vapour from the carbon canister, located in the rear drivers side.
     
    #4 David Beale, Nov 23, 2010
  5. ThaZiPSteR

    ThaZiPSteR New Member

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    I just stepped outside for a smoke and noticed this hissing sound. I thought a tire may be leaking air, so I got down under the car. The sound was coming from just in front of the spare tire well. A box with at least two wiring harnesses going into it. I did a quick search and it led me here. So I got in and pressed the power button to check the battery, and all looked well. I turned the power off, and rechecked. The sound was no longer there. This was not an electric motor sound, but a hissing like air being vented under pressure. I just wonder if this could be dangerous in any way?
     
    #5 ThaZiPSteR, Jan 17, 2011
  6. Fuel Miser

    Fuel Miser Junior Member

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    Nothing to worry about. Normal for all cars with the EVAP canisters on them.
     
    #6 Fuel Miser, Jan 17, 2011
  7. Airboss

    Airboss Junior Member

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    I experienced the buzzing noise last night. The car was parked for about 6 hours in the garage. It did sound electrical. I ran in to get the key, started the car, and no warning light or anything else unusual found. The car was quiet when turned off. I was afraid the battery would drain by morning. Weird!! Oh those crazy Prii.
     
    #7 Airboss, Mar 30, 2011
  8. Paradox

    Paradox Prius Enthusiast / Moderator
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    The manual talks about hearing noise about 5 hours after the car being shutting off.
     
    #8 Paradox, Mar 30, 2011
  9. mad-dog-one

    mad-dog-one Prius Enthusiast

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    Yes!
     
    #9 mad-dog-one, Mar 30, 2011
  10. twittel

    twittel Senior Member

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    No, it's not dangerous. It's only the fuel evap system doing check, but no fuel is being released.
     
    #10 twittel, Mar 30, 2011
  11. mad-dog-one

    mad-dog-one Prius Enthusiast

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    Stepping outside for a smoke is the dangerous part.
     
    #11 mad-dog-one, Mar 31, 2011
  12. priusFTW

    priusFTW Gen III JBL non Nav

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    Originally Posted by ThaZiPSteR [​IMG]
    I just stepped outside for a smoke ... . I just wonder if this could be dangerous in any way?


    I LOL out loud at that, thanks lol.
     
    #12 priusFTW, Apr 4, 2012
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