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What causes a loud "clunking" sound when the engine shuts off?

Discussion in 'Gen 2 Prius Main Forum' started by wbs887700, Jul 14, 2021.

  1. wbs887700

    wbs887700 Junior Member

    Joined:
    Jul 30, 2020
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    Location:
    USA
    Vehicle:
    2006 Prius
    Model:
    One
    My 2006 Prius is starting to make a loud noise when the engine shuts off while it is parked in ready mode. Like, when I have the AC running while I'm parked for example, and the engine shuts off.... It doesn't always do it, but often it makes that loud noise, and it shakes the car noticeably, when it shuts off. It almost sounds/feels like a stick shift car when it stalls out.

    What could cause this? I keep getting nervous that it's going to damage something, and ironically this all started after I used Lucas oil stabilizer with one of my past oil changes (I have drained it since and don't use it anymore//). Lucas oil stabilizer increases the thickness of the oil.

    How can I fix this?
     
    #1 wbs887700, Jul 14, 2021
  2. privilege

    privilege Active Member

    Joined:
    Mar 17, 2021
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    Location:
    Birmingham
    Vehicle:
    2011 Prius
    Model:
    Three
    First guess:
    motor mounts

    additional guesses:
    exhaust hanger
    worn suspension
    sloppy bearing somewhere (internal, expensive)

    get a friend to turn it on/off and watch the engine... does it rotate 4-5" when the CLANG happens ?
     
    #2 privilege, Jul 15, 2021
  3. PriusCamper

    PriusCamper Senior Member

    Joined:
    Mar 3, 2012
    10,955
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    Location:
    Pacific Northwest, USA
    Vehicle:
    2007 Prius
    Model:
    Two
    Atkinson engine's nature to have this glitch periodically...
     
    #3 PriusCamper, Jul 15, 2021
  4. edthefox5

    edthefox5 Senior Member

    Joined:
    Jul 25, 2007
    10,096
    4,795
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    Location:
    Clearwater, Florida
    Vehicle:
    2007 Prius
    Model:
    Two
    I noticed when my hybrid battery was getting ready to die it did not shut off or turn very elegantly. New battery much better.

    But many posts about bad motor mounts.

    what’s the deal with your hybrid battery is it the original?
     
    #4 edthefox5, Jul 15, 2021
  5. bradcarnage

    bradcarnage New Member

    Joined:
    Apr 21, 2023
    1
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    0
    Location:
    Fresno, California
    Vehicle:
    2006 Prius
    Model:
    II
    Any update on this? I picked up an 06 prius here and it's starting to show signs of that same issue.
     
    #5 bradcarnage, Apr 21, 2023
  6. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    7,035
    2,784
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    My C does this too.
    Barely noticeable and not all the time.
    From the responses here, it would appear that it really is NOT an "issue" unless it gets
    really LOUD.
     
    #6 sam spade 2, Apr 22, 2023
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