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2001 'Droning' noise

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by fjef, Aug 16, 2006.

  1. fjef

    fjef Junior Member

    Joined:
    Feb 20, 2005
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    Location:
    Ontario, Canada
    Vehicle:
    2001 Prius
    Model:
    I
    We have had 128,000 trouble free kms in our 2001 Prius. A couple of weeks ago, we took it in for the steering recall - the local Toyota dealer did a total check and even washed the car and returned it saying it was in great shape.

    Driving home from the dealer, I felt that there was slightly less power than usual and it just didn't feel 'right'. Over the next few days, a droning noise (kind of like the engine noise on a long haul 747 flight) started - it was very faint at first but has become louder. We took it back to the dealer who took 2 hours to check everything and it came back again newly washed and with their stamp of approval.

    In the last week, the noise has increased to the point where passengers are asking what the sound is. The sound itself is loudest when coasting and is not audible when accelerating. It is most pronounced when traveling about 40 to 70 kms/hr (25 to 45 mph) and when decelerating. The dealer said is was just the tires - but the noise is very loud now and is certainly not related to tire noise. We are experiencing a significant drop in fuel economy - from about 23 kms/litre to 18.

    Does this sound familiar to anyone? We called Toyota Japan HQ this morning and they suggest taking it in again - we are going back to the dealer later today but if I have some idea of what to point them to it may help them figure this out...
     
    #1 fjef, Aug 16, 2006
  2. c4

    c4 Active Member

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    Mar 29, 2005
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    Obvious things: did they affect the alignment when they did the steering? Did you lose any wheel weights on the tires and are the tires in good shape??

    I had an alignment done on my own 2001 a while back and ended up with a really loud droning, but only turning to the right. Going straight and turning left, everything was fine.. In my case, it was because the original alignment was quite a ways out and caused excessive wear on one portion of the tire and straightening it out now exposed a new section of the tire.. The noise disappeared over the next several thousand km as the tires wore in their new alignment positions..

    If all the above is OK, there's only one other thing that can drone like that, and that's the hybrid transaxle, and usually that's a sign of severe problems.. Don't let them return the vehicle a third time without getting to the bottom of what's causing the noise!!
     
    #2 c4, Aug 17, 2006
  3. jjbieler

    jjbieler New Member

    Joined:
    Sep 15, 2006
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    <div class='quotetop'>QUOTE(c4 @ Aug 17 2006, 09:25 AM) [snapback]304639[/snapback]</div>
    I had a droning sound similar to what you describe, and the Toyota dealer diagnosed an imminent failure of MG2, the motor-generator in the transaxle. This is a ~$5000 repair using factory parts. I am going to see if I can replace just the MG2, instead of the whole transaxle/inverter assembly.
     
    #3 jjbieler, Sep 18, 2006
  4. jjbieler

    jjbieler New Member

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    <div class='quotetop'>QUOTE(jbieler @ Sep 18 2006, 11:28 AM) [snapback]321171[/snapback]</div>
    Looks like MG2 is the major component of the transaxle, so I'm on the market for a salvage transaxle. The inverter is separate.
     
    #4 jjbieler, Sep 18, 2006
  5. tochatihu

    tochatihu Senior Member

    Joined:
    Apr 10, 2004
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    Location:
    Kunming Yunnan China
    Vehicle:
    2001 Prius
    fjef: check the wheel bearings
     
    #5 tochatihu, Sep 18, 2006
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