Hybrid battery humming, hours after car is turned off, normal???

Discussion in 'Gen 3 Prius Technical Discussion' started by Lisatsobo, Apr 24, 2016.

  1. Lisatsobo

    Lisatsobo Junior Member

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    Today I went in may garage and heard a humming from the rear of my 2014 prius. I assume it is the hybrid battery. This was several hours after the car had been driven. I turned the car on and then off and the humming stopped. Is this normal? I know it is common for it to hum immediately after you turn the car off for a bit, but several hrs later? Thanks for any help!
     
  2. bisco

    bisco cookie crumbler

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    normal, the car is talking. is anyone listening?

    but seriously, it's some kind of emissions check. nothing to worry about. scary the first time you hear it though.:p
     
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  3. WilDavis

    WilDavis Senior Member

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    Welcome to PriusChat! …as bisco mentioned I don't think there's anything to worry about! My Gen II does the same thing and I just put it down to the fact the car is "…having a quiet think", as I often times do myself, and when I hear my car doing it, I just creep quietly away so as not to disturb it, and let it get on with it! ;) :)
     
  4. ftl

    ftl Explicator

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    Read your owner's manual! You'll find something like this:

    Noise from under vehicle after turning off the hybrid system
    Approximately five hours after the hybrid system is turned off, you may hear
    sound coming from under the vehicle for several minutes. This is the sound
    of a fuel evaporation leakage check and, it does not indicate a malfunction.
     
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  5. wjtracy

    wjtracy Senior Member

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    Gee I guess that's what you get in a Gen3 to have the fixed gas tank whereas Gen2 we have a flexible gas tank. Kind of strange though, thinking of the rare but several incidents of fire after the car sits a while. Who knew the car scheduled after hours maintenance all by itself.
     
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  6. WyoNewk

    WyoNewk Junior Member

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    Interesting. I heard the same thing from mine a couple months ago. My wife came in from the garage and told me it was humming. I started it up and then shut it off. No more humming, but I was wondering what caused it. Now I know... sort of.
     
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  7. WilDavis

    WilDavis Senior Member

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    Have you stopped to consider that the reason it is humming is that it doesn't know the words? …just a thought! :confused: ;) :)
     
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  8. tv4fish

    tv4fish Member

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    That HAS to be it............................
     
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  9. Former Member 68813

    Former Member 68813 Senior Member

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    interesting idea about the fires. gas fumes and spark would do it indeed.
     
  10. macman408

    macman408 Electron Guidance Counselor

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    The fires reported here have mostly been in the front end of the car, far from the gas tank. I'm sure this system is unrelated. And I don't believe the Prius is unique in doing this; I wouldn't be surprised if it's required in California.

    Basically, it pumps air out of the fuel tank, and measures how quickly it leaks back in. If it leaks too quickly, there's a hole somewhere, or a seal isn't sealing, or the gas cap isn't on tight. The result is that evaporated fuel leaks into the atmosphere, which can contribute rather significantly to smog. The whole test cycle takes up to about 18 minutes or so. It runs at either 5, 7, or 9.5 hours after you turn off the car - whichever is the first time where the engine coolant is below 35°C.
     
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