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Knocking Sound on 2018 Prius Three

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by Daniel Dang, Feb 17, 2022.

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  1. Daniel Dang

    Daniel Dang New Member

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    Hi everyone. Anyone know what is the knocking sound come from when it is on P and still running. When the engine turn on for keep the battery sometimes the knocking sound happen twice and come with the felling like someone knock the car from behind. Is there anyone know what is that sign?
     
    #1 Daniel Dang, Feb 17, 2022
  2. jdenenberg

    jdenenberg EE Professor

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    The Prius transmission does not really have a neutral or a clutch so to simulate neutral there has to be a careful balance of one of the MGs and the ICE. When the ICE starts there will be a small imbalance which will be felt as a surge. There is some play in the parking pawl which allows some rocking so whenever the iCE starts your Prius will rock and there will be a clunk from the parking pawl and the drive train. You can ignore it as it is unavoidable.

    JeffD
     
    #2 jdenenberg, Feb 18, 2022
    bisco and Daniel Dang like this.
  3. Daniel Dang

    Daniel Dang New Member

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    Thank for the information Jeff. It happens when I switch to Parking. Can I avoid it by switch it to Neutral and hand brake?
     
    #3 Daniel Dang, Feb 18, 2022
  4. jdenenberg

    jdenenberg EE Professor

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    When you turn off power the parking pawl will engage anyway. If you use the parking brake, the Prius will not rock when the ICE starts and your symptoms will be gone.

    JeffD
     
    #4 jdenenberg, Feb 19, 2022
    Daniel Dang likes this.
  5. Daniel Dang

    Daniel Dang New Member

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    Thanks. I will try this way.
     
    #5 Daniel Dang, Feb 19, 2022
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    How many miles on it?
     
    #6 Mendel Leisk, Feb 19, 2022
  7. Hidyho

    Hidyho Senior Member

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    Will milage decide if there is a sound or not?

    Had an interesting sound situation, came in from a trip and when I got close to home, all of a sudden there was a horrible rubbing sound at the rear passenger fender, stopped to check and didn't see anything at first, then found a plastic piece at front side of bottom of rear wheel well had flipped sideways and was contacting tire. I have no idea what the piece was, or what it does, almost like a spacer piece at bottom of wheel well, just spun it back in place I think, but that cured that sound.
     
    #7 Hidyho, Feb 20, 2022
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