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Clunk sound when engine engages 2015 Prius V

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by Andrew Brousseau, Nov 26, 2023.

  1. Andrew Brousseau

    Andrew Brousseau Junior Member

    Joined:
    Mar 7, 2021
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    Location:
    Cape Ann, Massachusetts
    Vehicle:
    2015 Prius v wagon
    Model:
    III
    Hi all, my Prius makes one slight clunk noise when the engine engages during normal driving. This is when the engine is off (driving with battery or regening) then the engine comes on to supply drive power. Once the engine is on, it drives great.

    i don’t know how the engine marries to an already running drive train. But my sense is that mechanism re engaging is what is making that one clunk.

    I am at 100k miles and am going to replace the tranny oil with oem oil soon. I am guessing this is the first time it’s been done. I’ve owned the car since 60k. Is there anything I should look at while I have the plastic ‘skid’ plate off the bottom?
     
  2. BiomedO1

    BiomedO1 Senior Member

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    Vehicle:
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    Model:
    LE
    Check the condition of the half-shaft boots - torn or leaking. You may have an issue with the flex plate that connects the engine to the transmission. Unfortunately, you'll need to remove the transmission to replace it. Hopefully that's not the issue. Take it to a professional, experienced Prius mechanic, for a proper diagnosis.

    Good Luck......
     
    Tim Jones likes this.
  3. Andrew Brousseau

    Andrew Brousseau Junior Member

    Joined:
    Mar 7, 2021
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    Location:
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    Vehicle:
    2015 Prius v wagon
    Model:
    III
    Thanks, I will check those. The clunk is very slight right now.
    Is there any way to get eyes on the cv belt?
     
    Oldwolf likes this.
  4. gggGary

    gggGary gggGary

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    2023 Prius Prime
    Model:
    XSE Premium
    No expert but there's a damper plate twixt motor and planetary gear. Think I've seen it can have issues.
     
    Mendel Leisk, Oldwolf and Tim Jones like this.
  5. CR94

    CR94 Senior Member

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    Vehicle:
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    Model:
    Two
    I doubt that's a significant problem, unless it suddenly became a lot more noticeable. Due to backlash, there can be a slight "clunk" any time the direction of torque reverses on gears or joints.
     
    V Sport Wagon and Oldwolf like this.
  6. Tim Jones

    Tim Jones Senior Member

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    Vehicle:
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    ----USA----
    Trani might be getting bad................. I had to replace mine..... clunking was the first thing I noticed
     
  7. V Sport Wagon

    V Sport Wagon Member

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    Model:
    Five
    Transmission don't "go bad" unless you run them out of fluid from a leak or something. I've seen these flex plates that were put back in after an engine swap clunk more and make more noise after someone drove the car a long time on a blown headgasket with many many cold start rattles and shakes. Misfires with the shaking puts stress on that flex plate and damages the pressure plate and springs over time.
     
    Brian1954 likes this.
  8. Tim Jones

    Tim Jones Senior Member

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    Wow i didn't know you were with me in the car and serviced my trani.........
    Never (drove) it with a bad headgasket.......... no leak......... the noise was long before junk headgasket replacement
    But I have personally replaced the
    Inveter
    Transmission
    Brake System (firewall)
    Head Gasket
    Water Pump
    Traction Battery
    Have you?
     
  9. V Sport Wagon

    V Sport Wagon Member

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    I don't have to be with you in the car and service it, your mechanic just took you is all.
     
    #9 V Sport Wagon, Dec 15, 2023
    Last edited by a moderator: Dec 17, 2023
  10. rjparker

    rjparker Tu Humilde Sirviente

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    Vehicle:
    2012 Prius v wagon
    Model:
    Three
    There is no cv belt in a gen3 or newer Prius. The planetary gears are always engaged. One of the electric motors in the transaxle synchronizes rpm through the planetary gears to allow the engine to stop while the car is moving.

    The most common reason for a loud clunk or rattle when the engine starts is a misfire caused by a leaking head gasket.

    In early stages it only happens on cold starts but later on it can happen every time the engine turns on while driving. Usually most noticeable when taking off from a stop. Primarily due to reduced road noise.

    The noise comes from the damper due to a lack of sync between the engine and the transaxle. Caused by a misfire. Normally the damper is fine once the misfire is eliminated. A head gasket misfire is coolant fouling of the spark plug. That fouling is quickly burned off and typically does not last long enough to cause a check engine light.
     
    #10 rjparker, Dec 15, 2023
    Last edited: Dec 15, 2023