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3rd gen humming from engine

Discussion in 'Gen 3 Prius Main Forum' started by Pao Yang, Jan 23, 2019.

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  1. Pao Yang

    Pao Yang New Member

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    this noise almost sounds like when you are going downhill and you put the gear to B, and it charges the battery. anyone know what this could be? again it only happens at high speed around 55mph and you take your foot of the gas when exiting a ramp or curving through a ramp.
     
    #1 Pao Yang, Jan 23, 2019
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  2. amos

    amos Active Member

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    I noticed it happens when battery us 100% charged. So just push the gas pedal and o increaae speed .this will drain the battery and let the car out of B mode
     
    #2 amos, Jan 23, 2019
  3. DeezPrius

    DeezPrius Junior Member

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    thats your engine at a higher rpm load to assist with braking. Like when manual cars downshift without using the brakes. Its doing what its suppose to do.

    Edit .... "^the noise sound like" ... sorry for the mistake OP.
     
    #3 DeezPrius, Jan 23, 2019
    Last edited: Jan 23, 2019
  4. bisco

    bisco cookie crumbler

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    how many miles on her?

    when did the noise start?

    how many miles have you owned her?
     
    #4 bisco, Jan 23, 2019
  5. Pao Yang

    Pao Yang New Member

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    I bought the car new back in 2012. it have 147k now. i never change the 12v battery or change any spark plug. about a week ago up here in MN it’s cold averaging 10 degrees. when i start the car in the morning going to work the engine seems to struggle and hesitate to stay on(I’m thinking about putting in new spark plug and 12v battery) But still seems odd to me about that engine noise at high speed just because i took my foot of the gas pedal. This never happen before til after the engine thingy.
     
    #5 Pao Yang, Jan 23, 2019
  6. Pao Yang

    Pao Yang New Member

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    But the thing is I’m not in gear “B” or stepping on the brakes. Just like when you lift up your foot to decrease the speed. It shouldn’t sound like when in “B” mode going downhill using the engine to help brake/slow down the car.
     
    #6 Pao Yang, Jan 23, 2019
  7. DeezPrius

    DeezPrius Junior Member

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    @Pao Yang I would take it in to have it checked out. It could be a transmission whine where an internal bearing may be failing since its happening at higher speeds without load, or something with the engine itself. Hopefully it’s something minor and a quick fix.
     
    #7 DeezPrius, Jan 23, 2019
  8. bisco

    bisco cookie crumbler

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    you definitely need plugs, did you do any of the 120k maintenance?
     
    #8 bisco, Jan 23, 2019
  9. Pao Yang

    Pao Yang New Member

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    no i didn’t do the 120k service. I just been doing the every 5-10k service.
     
    #9 Pao Yang, Jan 23, 2019
  10. Pao Yang

    Pao Yang New Member

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    Just got done installing new NGK iridium spark plugs. Let’s see how it goes for the next couple of days
     
    #10 Pao Yang, Jan 23, 2019
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  11. amos

    amos Active Member

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    Whats the battery level when it happens? Is it full?
    At what speed does it happen?
    Can you see a charge to the HV battery or theres no charge?
    It happens to me a lot when battery is full. So i noticed that increasing speed a bit will stop it and since HV battery drains a little than this humming noise is gone.
     
    #11 amos, Jan 24, 2019
  12. Pao Yang

    Pao Yang New Member

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    Battery level almost full when this happens. This happens at speed around 50mph(doesn’t happen all the time,but this never happen before in my 7 year ownership ) I could see a charge going to the battery when this happens.
     
    #12 Pao Yang, Jan 24, 2019
  13. Pao Yang

    Pao Yang New Member

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    still humming from engine after new NGK spark plug install. But again it’s 1 degrees up here in MN today. windchill is negative 10. I’ve noticed the humming happens when it’s charging the battery
     
    #13 Pao Yang, Jan 24, 2019
  14. bisco

    bisco cookie crumbler

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    can you post a recording?
     
    #14 bisco, Jan 24, 2019
  15. DeezPrius

    DeezPrius Junior Member

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    @Pao Yang ... i'm not sure if it helps, but my prius is currently at the dealer for another issue, however, they stated that there are some updates to the vehicle. One of which is rough engine sound at startup. Diagnosis for irregular sounds is a hit/miss with forum communities unless its an occurring prevalence.
     
    #15 DeezPrius, Jan 25, 2019
  16. amos

    amos Active Member

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    50 mph is not so high. It seems like car goes to engine brake mode.
    Basically same like B mode.
    I know this is a strange advice but Try to shift into N for a short period. Noise will disapear. Or just drive faster.
    Thats what i do when my battery is fully charged and im on a steep downhill. Increasing speed drains the battery and stops " engine brake"
     
    #16 amos, Jan 25, 2019
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