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Unexplained Whirring, Whining Sound During Deceleration

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by cooltraders, Mar 20, 2016.

  1. cooltraders

    cooltraders Junior Member

    Joined:
    Apr 2, 2010
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    Location:
    St Petersburg, Florida
    Vehicle:
    2005 Prius
    Model:
    II
    I've posted a similar thread but I will now try to narrow this problem down a bit. My "05" Prius has 164K, I'm the original owner and I have had great success with this car. I know some owners talk about the loud whining humming sound from the A/C unit which I am aware of but this newest sound is different and after 4 hours with a Toyota tech all they can come up with is an A/C compressor going bad. I only hear this sound after I reach 40MPH+ and then decelerate. It then winds down with the speed of the car sometime intermittently. If I accelerate it goes quiet. I've also tried speeding up to 40MPH and then move into neutral. It will stop the noise. I'm adding a video and I realize there is standard road noise but if you watch my energy monitor you will hear the noise whirring winding when the green arrows point back to the electric motor. Pay close attention to the viseo frames at 13 seconds, 22 seconds and again at 29 seconds. Turn up the volume. Of course inside the cab it is much more pronounced. I'm finding it hard to believe this is an A/C compressor. Sounds more like an electric motor whining/whirring. Thanks for your help. I'm concerned about driving my car for safety reasons. Also, if anyone can identify the noise can you give me a solution?

     
    #1 cooltraders, Mar 20, 2016
  2. dolj

    dolj Senior Member

    Joined:
    May 14, 2012
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    Location:
    Wellington, New Zealand
    Vehicle:
    2007 Prius
    Model:
    N/A
    I don't hear anything out of the ordinary. There is the normal regen sound as the Motor/Generator comes under load.

    Could it be perhaps that the noise was always there and you have never noticed it? But now that you've noticed it, it you're focussing on it more?
     
    #2 dolj, Mar 20, 2016
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

    Joined:
    Mar 8, 2008
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    Location:
    Green Valley, AZ
    Vehicle:
    2015 Prius
    Model:
    Two
    The electric AC compressor is not the issue since the noise is affected by gear selector position. As you pointed out the noise goes away when you shift into N, it probably is caused by the transaxle, for example an MG1 bearing that is starting to wear out.

    Since you have no warning lights on, I would not worry about the noise. Just drive the car.

    If you see the red hybrid drivetrain warning icon appear in the upper left corner of the MFD, that is a good time to be concerned.
     
    #3 Patrick Wong, Mar 20, 2016
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