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Whining sound after shutdown

Discussion in 'Gen 2 Prius Main Forum' started by rogerthat, Jul 8, 2016.

  1. rogerthat

    rogerthat Active Member

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    Yesterday after a 45 minute drive home (GA and above 90 degree heat), I noticed a moderately high pitched whining noise after shutdown. The noise continued for about 5 minutes. From my understanding, the inverter coolant pump redistributes the coolant after shutdown and I have heard a humming noise previously which I assumed to be this action.

    However, this whining sound was different and appeared to come from the passenger side of the engine compartment (I'm not 100% sure the noise emanated from the passenger side, but it sure sounded like it) which is the opposite side to the inverter coolant pump. I know the ICE water pump is on the passenger side, but it was my understanding that this pump does not run after shutdown. A few hours later I took the car for a short 5 minute ride and could not hear the same noise after shutdown.

    Lastly, I also noticed a small amount of water that collected on the ground under the engine - I am assuming this is just condensation from the air conditioner unit, but I thought it was worth mentioning - clear non oily liquid - seemed to be water. Any help is appreciated.
     
    #1 rogerthat, Jul 8, 2016
  2. aaroncv3

    aaroncv3 Member

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    Not an engine pro, but sounds like a leaky gasket. was the pitch constant, or varying, particularly before ending?
     
    #2 aaroncv3, Jul 8, 2016
  3. rogerthat

    rogerthat Active Member

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    I think there was some variation, but I cannot honestly recall. I originally thought the noise was coming from my neighbor...but then after walking around my car I realized it was the Prius. I then popped the hood and the noise seemed to originate from the passenger side.
     
    #3 rogerthat, Jul 8, 2016
  4. aaroncv3

    aaroncv3 Member

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    my guess is water pump or thermostat. again, not a Prius ICE pro, but thermostat would likely be less expensive fix.

    monitor the level in your reservoir closely, before and after trips. just takes a second to look. if you notice a drop after a day or two, you can focus on the engine cooling system.
     
    #4 aaroncv3, Jul 8, 2016
  5. WilDavis

    WilDavis Senior Member

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    The small amount of water mentioned in your final paragraph is most likely to be condensate from the A/C unit, and is perfectly normal ofter prolonged use of the A/C - hope this helps - Wil
     
    #5 WilDavis, Jul 8, 2016
  6. bisco

    bisco cookie crumbler

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    how many miles on her?
     
    #6 bisco, Jul 8, 2016
  7. aaroncv3

    aaroncv3 Member

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    It just occurred to me. look for leaks on water hoses. be very careful, steam can burn you!
     
    #7 aaroncv3, Jul 8, 2016
  8. rogerthat

    rogerthat Active Member

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    2009 and only 60k miles on her. No noise today after driving in 90 degree + heat for about an hour. Can someone confirm that the ICE water pump does not run after shutoff. I have not noticed any leaking hoses.
     
    #8 rogerthat, Jul 8, 2016
  9. fotomoto

    fotomoto Senior Member

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    The ICE waterpump is mechanical and only runs if the ICE is running.
     
    #9 fotomoto, Jul 8, 2016
  10. Augustus88

    Augustus88 Junior Member

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    Could it be the AC compressor decompressing after it stops running?
    Could it be the radiator cap allowing coolant to expand into the overflow tank?
     
    #10 Augustus88, Jul 13, 2016
  11. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Gas tanks often have an emergency vent mechanism that'll activate on hot days, noticeable after shut down. And the liquid's very likely water condensate from AC use.
     
    #11 Mendel Leisk, Jul 13, 2016
  12. Fredii

    Fredii Junior Member

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    So whats the answer? The same happens with my 2009.
     
    #12 Fredii, Jun 10, 2022
  13. ChapmanF

    ChapmanF Senior Member

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    It's been six years, and the older situation wasn't described in very great detail (no recording of the sound, say, and it wasn't even clear what the OP meant by "after shutdown" ... after the engine shut down, or after powering off the whole car?).

    You'll probably get the best help if you back up a few steps and try to describe, as completely as you can, what your car is doing.
     
    #13 ChapmanF, Jun 11, 2022
  14. rogerthat

    rogerthat Active Member

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    Yep 6 years and the car is still making the same noise - very evident after driving with AC during a hot day and powering off the whole car. So I'm 99% sure its from the AC system - probably decompressing as Augustus88 suggested.
     
    #14 rogerthat, Jun 12, 2022
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  15. bisco

    bisco cookie crumbler

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    it's interesting, i don't remember anything after shut down on my '08
     
    #15 bisco, Jun 12, 2022
  16. rogerthat

    rogerthat Active Member

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    To be honest, I pretty much forgot/ignored the issue as the car still drives well and the AC works. However, now that this thread has resurfaced, I recall pinpointing the noise as coming from the below AC component - I recall wondering if this component was unique to 2009 models, but I never checked. Maybe some type of pressure relief valve or is this simply where refrigerant is added??

    AC Component.jpg
     
    #16 rogerthat, Jun 12, 2022
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