Loud fan noise when turning on

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by Joe Dipierro, May 17, 2026.

  1. Joe Dipierro

    Joe Dipierro Junior Member

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    So a few months ago I noticed a loud noise when the engine would first kick on, maybe 3 different occasions. Didn’t think anything of it and then I heard it again the other day and today I heard it multiple times through the day. Mind you it was a hot day and I was in my car quite a bit today. I was parked and the engine goes off and comes back on and I hear the fan. It almost sounds like it’s gonna break but then it’s okay. Anyone know what this is or anyone else experiencing this issue? 2016 Prius here with over 242,000 miles on it now.
     
    #1 Joe Dipierro, May 17, 2026
  2. rjparker

    rjparker Tu Humilde Sirviente

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    If you are parked using the ac the radiator fans are very likely coming on in high speed. Best thing to do is open the hood and observe.
     
    #2 rjparker, May 17, 2026
  3. Joe Dipierro

    Joe Dipierro Junior Member

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    Alright next time I have the chance I will, I’m not very mechanically inclined but I’ll try to see where the noise is coming from. Thank you
     
    #3 Joe Dipierro, May 17, 2026
  4. Mendel Leisk

    Mendel Leisk MMX GEN III

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    To clarify, this is the fans behind the radiator, in the engine bay? (My first thought was the cabin vent fan, and rodents...)
     
    #4 Mendel Leisk, May 18, 2026
  5. Joe Dipierro

    Joe Dipierro Junior Member

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    I also had exhaust the last two mornings but only for a short time. Well on my way home from work I kept hearing the clanking noise or whatever coming from under the hood and my car literally died. Wouldn’t drive anymore. I got a message about a hybrid system malfunction. Had to get it towed to a shop I’m praying it’s nothing too serious.
     

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    #5 Joe Dipierro, May 20, 2026 at 12:13 AM
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  6. Mendel Leisk

    Mendel Leisk MMX GEN III

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    2016 model year is first year of gen 4, prone to coolant leaks in the exhaust heat recovery system, engine can run out of coolant. Just one possibility.
     
    #6 Mendel Leisk, May 20, 2026 at 7:09 AM
  7. ChapmanF

    ChapmanF Senior Member

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    Wait, in the title you said a fan noise, now you kept hearing the clanking noise? Is that a new, different noise, or were you saying a fan was clanking?
     
    #7 ChapmanF, May 20, 2026 at 11:17 AM
  8. Joe Dipierro

    Joe Dipierro Junior Member

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    I’m really not sure but the mechanic told me the transmission chain went and that to get a used one would cost 5000$. Not sure if I should fix or not
     
    #8 Joe Dipierro, May 22, 2026 at 10:19 AM
  9. rjparker

    rjparker Tu Humilde Sirviente

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    There is no transmission chain. Hybrids confuse a lot of conventional mechanics.

    Get a new mechanic or at least have it diagnosed by a dealer.
     
    #9 rjparker, May 22, 2026 at 12:06 PM
  10. ChapmanF

    ChapmanF Senior Member

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    Gen 1 and 2 had a chain. Maybe the mechanic was remembering that.
     
    #10 ChapmanF, May 22, 2026 at 1:26 PM
    Last edited: May 22, 2026 at 1:36 PM
  11. frodoz737

    frodoz737 Top Wrench

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    You need a qualified mechanic.
     
    #11 frodoz737, May 22, 2026 at 4:10 PM
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