What is this odd sound coming from my engine area?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Charley Gosse, May 23, 2023.

  1. Charley Gosse

    Charley Gosse Junior Member

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    While driving my Prius 2006 I hear this low ringing sound every 12 seconds and the sound is audible for 4 seconds, stops, and then 12 seconds later I hear it again and this goes on and on and continues for a few minutes after I turn off the car. It's like someone put a little alarm clock behind my dashboard in my engine compartment and it rings for 4 seconds. Is it a pump? Here is a link to an "M4A" sound file.
    https://1drv.ms/u/s!Aq298eFp-zvBmORZnlAAoo_XmK1CZw?e=ErmykI

    Here is a photo of the part of the engine compartment it seems to be coming from.
    https://1drv.ms/i/s!Aq298eFp-zvBmORaHAafLcUqyxy7LA?e=NDfeqG

    Please let me know what you think it is and if it's ok or something I need to get checked-out.
    Charley
     
    #1 Charley Gosse, May 23, 2023
  2. spdracrm3

    spdracrm3 Member

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    There is a pump that runs after shut down to fill the thermos bottle with hot engine coolant but thats in left front behind the left headlight.
    I dont know what would be back there that would run, whatever it is doesnt sound healthy maybe take to a shop and have them listen with a stethoscope to locate the culprit.

    SM-G960U ?
     
    #2 spdracrm3, May 23, 2023
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  3. ChapmanF

    ChapmanF Senior Member

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    The "live.com" link fights me, but without even listening, your description sounds like the electric pump that repressurizes the brake system.

    After you have been away from the car for some hours, listen carefully when you first open the driver's door. Hear the same sound?

    Then mash the brake pedal several times, and see if the sound comes back, sooner than it does when you're not using the brakes.

    I'm guessing you'll confirm that's what it is. When it has to repressurize over and over even when nobody's using the brakes, there is a leak, typically an internal one, where the pressurized fluid just escapes back to the reservoir, and nothing is leaking out of the car. There are lots and lots of threads here about it.
     
    #3 ChapmanF, May 23, 2023
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  4. Charley Gosse

    Charley Gosse Junior Member

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    ChapmanF, I tried this and what you expected did happen though the interval between the sound was about 24 seconds and the sound was only about 2 seconds and that repeated.
     
    #4 Charley Gosse, May 25, 2023
  5. ChapmanF

    ChapmanF Senior Member

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    If nobody's touching the brakes, the pressure normally holds for more like hours before the pump has to run again, so a period of 24 seconds qualifies for an "it's dead, Jim."
     
    #5 ChapmanF, May 25, 2023
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  6. Charley Gosse

    Charley Gosse Junior Member

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    Mr. Chapman,
    Just to be clear, as soon as I open the driver's-side door in the morning, the sound begins and runs for maybe 4 seconds. I then depress the brake and press the start button to start the car and the sound runs again and then stops after maybe 4 seconds.
     
    #6 Charley Gosse, May 25, 2023
  7. ChapmanF

    ChapmanF Senior Member

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    Good to know. And just to complete the picture, what did this part ("the interval between the sound was about 24 seconds") in your post #4 mean?
     
    #7 ChapmanF, May 25, 2023
  8. Charley Gosse

    Charley Gosse Junior Member

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    I meant that the reservoir pump sound is off for 24 seconds and then runs for 2-3 seconds.
     
    #8 Charley Gosse, May 26, 2023
  9. ChapmanF

    ChapmanF Senior Member

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    When no one is using the brakes, the time the pump stays off should normally be hours, not 24 seconds.
     
    #9 ChapmanF, May 26, 2023
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  10. ColoradoCrow

    ColoradoCrow Senior Member

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    The pump is running to pressurize the system. Once pressure builds up it shuts off. Then you use the pressure to run the brakes and stop the car....or if you don't touch the brake pedal AT ALL....and the pressure leaks out and drops below the correct level.....the pump kicks on and runs again to build the pressure back up. This cycle continues. If your pumps runs often with short time between running....your ABS Pump Assembly is starting to fail and you will eventually feel the lack of pressure in the brakes and the car will be difficult to stop...then impossible and dangerous to drive. ie CRASH!!!! Solution is to replace unit with a used one......which will also fail (eventually) or with a new one. New one here.
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    #10 ColoradoCrow, May 26, 2023
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