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Weird Acceleration Thump

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by slowsword, Apr 16, 2016.

  1. slowsword

    slowsword New Member

    Joined:
    Apr 16, 2016
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    Location:
    FL
    Vehicle:
    2009 Prius
    Model:
    Four Touring
    Purchased an 09 Touring and so far enjoying the driving experience. Getting 42/43MPG with mostly short trips. However, I have noticed one thing unusual. Not sure if I should be concerned or if this is a normal thing. I am a rideshare driver, and whenever a group of people get out and I accelerate away from them, I hear a pretty loud thump sound. This happens usually when a group of 3 or more exits and often does not happen when one or two people exit the vehicle.

    I'm inclined to believe that it's either:

    1. Bad engine/transaxle mount

    Or

    2. Suspension issue as this noticeable usually after a heavy payload has left the vehicle.

    If anyone can enlighten me on this issue, I would greatly appreciate it!
     
    #1 slowsword, Apr 16, 2016
  2. andrewclaus

    andrewclaus Active Member

    Joined:
    Sep 15, 2009
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    Location:
    Golden, CO
    Vehicle:
    2007 Prius
    It sounds like the common denominator is when the back seat is loaded. I'd look at rear suspension, but don't neglect the front. Bounce on struts (front) and shocks (rear), see if you can recreate the noise. Rotate the tires and check tightness of all suspension pieces. Secure the car on jackstands and use a small crowbar and large pair of channellock pliers to pry on and squeeze bushings and joints. (Stay away from brake lines and ABS sensors!) It would be a good time to pull rear brake drums for a check, and make sure they're in adjustment.

    Can you tell a quadrant from where the noise is coming? You suspect engine mount, does that mean it sounds like it's coming from under the hood? If you can observe engine/transaxle movement when the engine starts or stops, have the mounts checked.

    The noise could be significant. It's never a good idea to ignore suspension noise.
     
    #2 andrewclaus, Apr 16, 2016
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

    Joined:
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    Location:
    Green Valley, AZ
    Vehicle:
    2015 Prius
    Model:
    Two
    That is not normal, and sounds like a problem with your rear shocks and/or the rear springs. Maybe a spring is broken. Get under the rear of the car and inspect them.
     
    #3 Patrick Wong, Apr 16, 2016
  4. slowsword

    slowsword New Member

    Joined:
    Apr 16, 2016
    2
    0
    0
    Location:
    FL
    Vehicle:
    2009 Prius
    Model:
    Four Touring
    Thanks guys. I am going to take it in for a diagnosis this week. Hopefully wouldn't have too much trouble finding a group of guys to replicate the problem.
     
    #4 slowsword, Apr 20, 2016
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