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Help - Louder than normal regenerative braking 27 to 7 MPH

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by DG Bear, Aug 17, 2016.

  1. DG Bear

    DG Bear Junior Member

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    Car makes louder than normal regenerative braking (Hybrid Sound). Seems normal when braking at high speeds... then when the speed drops below 30mph the sound is noticeable louder. See Video for example sounds while braking (17, 35 and 50 seconds into the video are most notable).


    https://youtu.be/KhiqP-DAx5U

    Car drives normal other than the regenerative braking sound...

    Note: Car was involved in a front end accident. Damages were repaired and seem minor. Front Bumper cover, hood, Radiator, Fans, RF Fender. Front cross member and other frame areas look untouched.

    Any input greatly appreciated.
     
    #1 DG Bear, Aug 17, 2016
  2. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Does sound funny. Maybe something to do with the radiator repair? The inverter radiator is at the top, a few inches in height? Maybe the inverter is not cooling properly??
     
    #2 Mendel Leisk, Aug 17, 2016
  3. DG Bear

    DG Bear Junior Member

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    No... I don't think so. No codes to indicate a inverter temp problem.
    Weird thing is the sound gets abnormal only in then 25 and below mph range
     
    #3 DG Bear, Aug 19, 2016
    Last edited: Aug 23, 2016
    Mendel Leisk likes this.
  4. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    I'll bow out, sounds like you're really on it, reading codes and all.
     
    #4 Mendel Leisk, Aug 19, 2016
  5. Starship_Enterprius

    Starship_Enterprius Active Member

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    Over a decade ago, I felt the MG's in my G1 were getting a teeny witty bit louder. I feared one of the MG rotors were off centered and didn't believe when the dealer told me it was a wheel bearing. I let them change them anyway as they were still under warranty. Lo and behold, the noise disappeared! Just a long shot.... maybe the increased regen at lower speed is making a worn bearing sound louder.
     
    #5 Starship_Enterprius, Aug 19, 2016
  6. Kenny94945

    Kenny94945 Active Member

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    Well...the video is good evidence.

    To me it sounds like the brake pads grabbing the rotor.
    OEM pads?
    Best I can offer...remove the calipers and inspect the brakes including rotor runout.
    Doesn't sound to me like anything is broken
    Yet not necessarily a normal sound as compare to other Priuses.

    Good hunting.
     
    #6 Kenny94945, Aug 20, 2016
  7. DG Bear

    DG Bear Junior Member

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    Thanks for the feedback.
    I have another Prius that had a bad wheel bearing.... I think I would recognize that sound.
    In my experience... the wheel bearing sound was very distinct and varied when you add more/less stress by turning the wheel. It also got louder as you increased speed. The sound was a much lower frequency / roaring sound.

    This sound reminds me of the electric motor sound you hear in a prius and in a electric bus.

    Did your wheel bearing sound like the one in the video?
     
    #7 DG Bear, Aug 23, 2016
  8. bisco

    bisco cookie crumbler

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    sounds like an axle tranny problem, but i don't see how they could have been affected by the accident. how many miles on her?
     
    #8 bisco, Aug 23, 2016
  9. DG Bear

    DG Bear Junior Member

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    Thanks for your input... the Pads are OEM

    I don't think its the rotor as they are not involved at that speed (above ~8 mph?... unless you are braking hard). Also the rotors are involved when you drop below 7 mph and at that time the sound disappears. To me the sound is similar to the "hybrid / electric motor" sound that the other two Prius I have make when the electric motor is accelerating and used for regenerative braking... it's just odd that its more pronounced that the 27 - 7mph.

    If you listen carefully you can hear a change in pitch or pulsating sound at times.
    60k
     
    #9 DG Bear, Aug 23, 2016
  10. Starship_Enterprius

    Starship_Enterprius Active Member

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    Yup it did sound similar to regen sound but just a wee bit louder. A high whining sound - the same when an electric motor bearings start to whine. I'm quiet familiar with wheel bearing grind because I keep my cars 10 to 16 years and run them to the ground :D..... so it must've been at a very early stage of failure because it didn't sound like one. And since it was 2003 and hybrids were unproven, I freaked out and thought it was one of the MG's. Anyway, it's just a remote possibility. Next time you jack your car just spin your wheels to check.
     
    #10 Starship_Enterprius, Aug 24, 2016
  11. DG Bear

    DG Bear Junior Member

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    That's an interesting point "A high whining sound - the same when an electric motor bearings start to whine"

    Are you saying that the sound on the video is similar to what a bad MG bearing would sound like?

    I would have to admit I do not know what to expect from bad bearing in the MG's. My experience with bad bearing on an electric motor comes from my pool pumps (and in that case the pool pump sound is quite different from this "hybrid" sound).
     
    #11 DG Bear, Aug 24, 2016
  12. Starship_Enterprius

    Starship_Enterprius Active Member

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    I'm no an expert on electric motors either, so that's what I think they would sound. My experience coming only from worn room floor fans and car blower motors going bad.
     
    #12 Starship_Enterprius, Aug 25, 2016
  13. CR94

    CR94 Senior Member

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    Electric motor bearings don't necessarily make any sound you can hear. Failing or inadequately lubricated sleeve bearings may screech or chatter. Failing rolling-element bearings may roar (like bad wheel bearings, for example).
     
    #13 CR94, Aug 25, 2016
  14. Starship_Enterprius

    Starship_Enterprius Active Member

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    Thanks.... so I guess from my untrained ear, the very early stage of the bearing sleeve screeching is what I mistake as whining.
     
    #14 Starship_Enterprius, Aug 26, 2016
  15. DG Bear

    DG Bear Junior Member

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    I'm not sure if the sound is associated with the accident.

    It may have had the sound before the accident... if one is not familiar with the Prius sounds they may thing this is just one of the normal Prius sounds and not an issue.

    Ironically I have two other 2010 Prius cars... one is quite quiet and the 2nd one (Prius #2) makes a noticeably louder hybrid sound. Prius 2 is definitely louder that Prius #1 or Prius #3. The odd thing is the louder sound below 27mph (and only when braking).
     
    #15 DG Bear, Aug 27, 2016
  16. DG Bear

    DG Bear Junior Member

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    Do you thing the sound that gets louder below 27 when braking is a electric motor bearing sound?
     
    #16 DG Bear, Aug 27, 2016
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