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Strange hooting noise under the hood

Discussion in 'Gen 2 Prius Main Forum' started by andyg, Apr 12, 2017.

  1. andyg

    andyg Junior Member

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    Of late, I hear a strange repetitive hooting noise under the hood towards the driver side whenever ICE shuts down. I can also hear it sometimes when driving, but hard to hear when ICE kicks in. The noise is different from the ratchet sound of the water pump you hear when the engine is off. This new noise sounds more like a repetitive owl hoot. I have 180K miles on my 2008 Gen II Prius and it drives like a charm otherwise. AFAIK, the water pumps are original including one early recall replacement. I monitor water temp regularly on my scanguage II and it is steady around 184°F. My battery SOC also holds fairly steady at 65%.

    I'd greatly appreciate any advice help explain the new noise. For the last couple of years I have been doing my own oil change using Mobil 1. I would try to fix this noise issue myself if there are any suggestions. I will be attempting both coolant changes soon as the weather gets a bit warmer.

    Thanks in advance
     
    #1 andyg, Apr 12, 2017
  2. JC91006

    JC91006 Senior Member

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    The noise is from the coolant pump that pumps coolant into and out of the thermos when the car is turned on and off
     
    #2 JC91006, Apr 12, 2017
  3. andyg

    andyg Junior Member

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    Thank you for your quick response. Is the pumping noise normal? It was not audible all these years which set me wondering if something like the pump is nearing failure.
     
    #3 andyg, Apr 12, 2017
  4. JC91006

    JC91006 Senior Member

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    It does that as the car ages. Mine has been doing it for 3 years. It's only for about 10 seconds so it's not worth spending money to change the pump
     
    #4 JC91006, Apr 12, 2017
    andyg likes this.
  5. Mr Mik

    Mr Mik Junior Member

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    I'm not convinced Andy and JC are talking about the same noise.

    I think I MIGHT be hearing the same noise as Andy, also produced by a 2008 NHW20, now 220000km old and running very well.
    I hear the noises when stopped at traffic lights etc.
    The noise is intermittent, just loud enough to hear it when it's otherwise quiet (no radio on etc), and to me it sounds like a very brief honk of a car horn. 'Repetitive owl hoot' as Andy called it is also a good description for it. It last less than 1/2 a second at a time. Sometimes it happens every couple of seconds, sometimes I don't hear it for days. The sounds frequency is maybe around 300-500Hz.
    I tried to listen to it with the car parked and the bonnet open, but the Prius refuses to cooperate and I only hear the noise while temporarily stopping during a drive. Everyone else in the car hears it too, just in case you are wondering..... ;-)
     
    #5 Mr Mik, Jun 8, 2017
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