What the hell is this noise

Discussion in 'Gen 2 Prius Technical Discussion' started by Toddwilks, Jan 21, 2021.

  1. Toddwilks

    Toddwilks Active Member

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    What the hell is this noise. It’s the high pitch buzzing/whining. This happens at all speeds up to even 68mph. It happens whenever I am on the gas (even lightly) or when coasting to slow down. It changes pitch when I start applying brakes again even lightly. The noise is there on EV and on hybrid mode. Battery is 76% life left. No codes per Techstream health check. This is not normal.




    iPhone ?
     
    #1 Toddwilks, Jan 21, 2021
    Last edited: Jan 21, 2021
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  2. ChapmanF

    ChapmanF Senior Member

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    I don't hear any obviously abnormal noise there.

    The hybrid system does modulate power by switching the high-voltage DC on and off at a high switching rate, enough to hear as a high-pitched whine. It can be heard, more or less faintly, from all areas where the HV wiring passes (the switched currents generate magnetic fields, the wires pass near steel surfaces like the floor of the car, so some vibrations are produced, i.e. sounds).

    How audible they are can depend on different things. There was a while I was driving my Gen 1 with the back seat removed, and the whine was very audible then from the battery area. I had never noticed that when the seat was in place. You haven't mentioned exactly where you're hearing the whine the most, or whether you've made any changes to trim or upholstery or what cargo you're carrying, but those might be things to think about.

    Out under the hood, the loudest whine I usually hear is from the throttle body. That's not high voltage, it runs on 12 volts, but is controlled by pulse modulation the same way, and makes a very noticeable whine. There is a loop of coolant flowing through the throttle body, and water conducts sound like magic, and the coolant plumbing runs kind of all over the engine compartment, meaning that throttle body whine often sounds like it's coming from everywhere under the hood. With a mechanic's stethoscope it's easy to confirm the throttle body is the source.
     
  3. PriusCamper

    PriusCamper Senior Member

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    I can't hear any problem sounds of not in video... Probably due to my lousy laptop speakers. If the noise can still be heard even when the engine is off and you're just sitting there have a look at purging the air from inverter pump cooling system. If that's not the problem, then please give us more details?
     
  4. Toddwilks

    Toddwilks Active Member

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    The noise is coming from in the engine bay. I’ve noticed if I put the car in neutral while coasting the noise goes away. As soon as it’s back in drive it’s back so it made me think a tranny issue. I haven’t changed the trans fluid yet nor checked it so maybe that is it, not enough or something. No record if the previous owner changed it. No interior changes were made, completely stock


    iPhone ?
     
  5. Toddwilks

    Toddwilks Active Member

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    No noise when not moving and engine running

    No noise when not moving and on battery power.


    iPhone ?
     
  6. ChapmanF

    ChapmanF Senior Member

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    Maybe you could use some DAW software on your recording, and emphasize the noise you are concerned about? Two of us have listened now, through our respective speakers, and not picked out any sounds our cars don't make because they're happy.

    If you think it might be from the tranny, and it's not there when the car is stopped, with or without the engine running, that also rules out anything in the tranny ahead of MG2 and the final drive.

    If your sound is mechanically produced in the tranny that way, it should have a pitch proportional to road speed. Not just that might be somewhat different at different speeds, but that actually rises and falls in pitch in direct proportion to road speed. If not, you've probably ruled out that cause. Otherwise, by looking carefully at the pitch and the road speed, you may get a clue as to which component of the tranny. Here's an old thread that might give you ideas.

    Also, you might find a shop that has this app (from the same guy who does the informative Weber Auto videos) that's based on the same principles and does a lot of the pencil-pushing for you.

     
  7. fotomoto

    fotomoto Senior Member

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    G2 is known for wheel bearings so I'd give those a good check.
     
  8. Toddwilks

    Toddwilks Active Member

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    Checked and they’re good. It’s interesting I listen to the video on my iPhone and the buzzing is clear as day when I listen to it on YouTube. Within the first 15 seconds you can hear me pulsing the gas pedal and making the noise


    iPhone ?
     
  9. Toddwilks

    Toddwilks Active Member

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    I’m going to try and put my GoPro under the hood and drive with it recoding.


    iPhone ?
     
  10. ChapmanF

    ChapmanF Senior Member

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    By coincidence, in another thread, Elektroingenieur recently posted a Toyota training video on Noise, Vibration, Harshness diagnosis that goes into more of the principles.
     
  11. PriusCamper

    PriusCamper Senior Member

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    Try putting a magnet on the transmission drain plug and running the engine around town for a little while and then changing out the fluid. If something is braking inside maybe you'll be able to pick some fragments of it with the magnet on the drain bolt?
     
  12. jerrymildred

    jerrymildred Senior Member

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    I listened with noise canceling headphones with the noise cancelling on and off. I didn't hear anything unusual. In fact, I heard less than usual. All six of our Prii have had a pronounced electrical whine from the inverters and electric motors. It's especially loud in my Prime and it's just the normal noise electric motors make. It seems loudest when coasting or braking. Since you said it changes when you brake, that pretty much convinced me that that's what it is.
     
  13. Aaron Vitolins

    Aaron Vitolins Senior Member

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    I’m with you on this. Out of my 4 Prii, this is very normal. My moms Lexus rx450h makes much more electric motor noise while cursing down the road, and even that is very faint.
     
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  14. PriusCamper

    PriusCamper Senior Member

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    I also notice on my 2007 that certain AM radio stations will pick up a tiny bit of noise from the electric motors... So make sure your radio is turned off, though I suspect you already handled that.
     
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  15. Toddwilks

    Toddwilks Active Member

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    Yup I even unplugged it to be certain.


    iPhone ?
     
  16. ChapmanF

    ChapmanF Senior Member

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    At this point, if the noise still concerns you, I'd repeat the suggestion about you using some DAW software on your own to post a recording where you have brought out the particular noise that concerns you. Several of us listening to the raw audio still haven't picked out what you're focusing on, so that could help a lot.
     
  17. jerrymildred

    jerrymildred Senior Member

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    AM radio sure is sensitive to any kind of arcing/sparking. Back in the old days of ignition systems that used points, I used to use an AM radio tuned between stations to set the timing on my motorcycles. Turn the crank with a wrench and listen for the snap.
     
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  18. ChapmanF

    ChapmanF Senior Member

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    If you were playing TREK80 on a Sol,

    [​IMG]
    [​IMG]

    then, for the sound effects, you put an AM radio next to the computer.

    Various timing loops in the program made the trek sounds.
     
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  19. edthefox5

    edthefox5 Senior Member

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    I don’t hear anything.

    start digging around. Change the trans fluid. The dump bolt has a magnet on it so you can see if it is having any bear issues.
    Please don’t show us the color of the fluid we have seen literally thousands of those.

    replace the inverter fluid if car is new to you replace the inverter pump too a high failure item. My pump just failed recently.

    check the engine oil after the car has sat for a while. Keep the oil right at the full line so you can see how much oil it’s eating. It’s eating oil you just have to figure out how much or lose the engine.

    Replace the water pump belt when it’s off spin the water pump and idler see how noisey there bearings are.

    if you want to check the engine go on YouTube and search

    Prius inspection

    it will show you how to turn the engine on in idle and will idle until the car is shut off. Very handy to check the health of the engine.
     
  20. ChapmanF

    ChapmanF Senior Member

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    One approach is to buy, do, dig, and replace a whole lot of things, in the hope that somewhere in all of that buying, doing, or replacing, you will happen to learn something about the noise that concerns you.

    Another approach would be to buy, do, dig, and replace a whole lot less stuff, and just concentrate on trying to learn what you can from and about the noise. Try to get a better recording of it (you were going to stick the GoPro under the hood, right?). Pick up an inexpensive mechanic's stethoscope, or maybe even rent a ChassisEar, and work on localizing where the sound is coming from. (Often, it will sound very different through a stethoscope or ChassisEar than it sounds through the air, and sometimes the different sound will give you ideas.) Put the best recordings you've got on a computer and work with them to isolate and analyze the sound.

    That might lead to useful revelations about your noise without even having to buy and do and dig and replace a whole lot of stuff, or risking the minor or major annoyances or complications that can arise in doing all that stuff. (A good word of the day is 'iatrogenesis', whenever you're trying to chase down one problem you already have by diving into lots of scattershot wrenchery.)
     
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