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Electric motor noise when braking

Discussion in 'Gen 3 Prius Technical Discussion' started by white2011, Oct 4, 2011.

  1. white2011

    white2011 Junior Member

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    First time positing... Only 1,000 miles on our one month old 2011...

    I hear a distinctive electric motor noise -- similar to the electric antenna noise in our 4Runner -- almost always immediately after applying the brakes (no matter whether hard or soft). The noise lasts maybe one or two seconds.

    I've also heard it right after unlocking the car first thing in the morning, before I've even sat down in the seat much less started the car. It sounds like it could be an electric pump creating brake line pressure. Is there such a thing? Does hearing it so often indicate some kind of leak?

    EDIT: In a subsequent post about 5 or 6 down I've attached an audio file you can download to hear the sound I'm talking about.
     
    #1 white2011, Oct 4, 2011
    sri81 likes this.
  2. pfjmarina

    pfjmarina Junior Member

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    Not sure about the noise you hear when braking, but the pump noise you hear when you open the driver side door before getting in is indeed for pumping pressure into the brake lines. It's completely normal.

    I doubt you're leaking any fluid, but maybe put a big piece of cardboard underneath the engine compartment for a few days to check.

    Enjoy your new Prius! We've had ours about six months and absolutely love it:D
     
    #2 pfjmarina, Oct 4, 2011
  3. white2011

    white2011 Junior Member

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    I found this thread using google. I tried to include a link to it, but I got the following error:

    So copy/paste this into your browser URL box:

    priuschat.com/forums/gen-ii-prius-care-maintenance-troubleshooting/51547-noise-when-braking-even-when-engine-off.html

    Anyway, apparently it's the "brake pressure accumulator pump."

    I'll try to learn to ignore it, but it's hard because it sounds "unhealthy".
     
    #3 white2011, Oct 4, 2011
  4. jdcollins5

    jdcollins5 Senior Member

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    Have you heard of regenerative braking? That is when the electric motor reverses current flow to slow the car down and charge the hybrid battery. That is why you hear the electric motor noise. Perfectly normal and what you paid for with a hybrid vehicle. When on the HSI screen it is when the bar goes to the left in the Charge area.

    You are correct on this one. It is the brake accumulator pump starting to build up pressure before you are ready to drive away. Smart car huh? Once again it is normal and what you paid for with the Prius. No extra charge for either :)

    You really need to read your Owner's Manual and learn more about your new car. Also there are a lot of good articles on this website that will help.
     
    #4 jdcollins5, Oct 4, 2011
  5. Teakwood

    Teakwood Member

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    What "jdcollins5" said.
     
    #5 Teakwood, Oct 4, 2011
  6. Feri

    Feri Active Member

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    #6 Feri, Oct 4, 2011
  7. white2011

    white2011 Junior Member

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    Okay, I've added a zipped Quicktime audio file (.m4a) to this post captured while stopped in Park and repeatedly pressing the brake pedal every few seconds.

    To listen to it you need to download it, unzip it, and open it with Quicktime (standard on Mac, downloadable for free on Windows).

    You can hear the distinctive noise several times, :03-:05, :10-:11, :15-:16, :17-:19 and :23-:25.

    Does every one else's Prius make this sound when you press the brake repeatedly when stopped in Park?
     

    Attached Files:

    #7 white2011, Oct 5, 2011
  8. xpcman

    xpcman Senior Member

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    I have never felt the need to "press the brake repeatedly when stopped in Park". I will try it on my 2010 today.

    Confirmed - on the second push I get that noise.
     
    #8 xpcman, Oct 5, 2011
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  9. white2011

    white2011 Junior Member

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    Thanks! Now that I've brought your attention to it, I apologize in advance if you now find it difficult to ignore and are annoyed by it. Sorry!!!
     
    #9 white2011, Oct 5, 2011
  10. adamace1

    adamace1 Senior Member

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    normal operation.
     
    #10 adamace1, Oct 5, 2011
  11. cwerdna

    cwerdna Senior Member

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    Sounds normal to me. My 2nd gen makes a similar noise. I've confirmed noises that sound like this on 3rd gens I've test driven.

    You should be able to repro this by pumping the brakes even w/the car's power off.
     
    #11 cwerdna, Oct 5, 2011
  12. chucko

    chucko Junior Member

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    I received a DVD as part of the owners manual pkg with my new 2011. If you received one, give it a view as it explains all of the different sounds that your Prius will make during normal operation.
     
    #12 chucko, Oct 9, 2011
  13. PaJa

    PaJa Senior member

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    The sound is brake pressure pump noise. If you hit the brake pedal, you lower the pressure in the system and the car needs to increase it. Pretty standard noise - don't worry.
     
    #13 PaJa, Oct 10, 2011
  14. Eoin

    Eoin Active Member

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    My 2010 makes these pumping sounds every time I push the brake but my 2005 is completely silent. The 2005 brakes are also stronger.
     
    #14 Eoin, Oct 21, 2011
  15. PaJa

    PaJa Senior member

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    Lets try to visit a dealer - it is not a standard behaviour. May be the system needs some tuning.
     
    #15 PaJa, Oct 25, 2011
  16. qbee42

    qbee42 My other car is a boat

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    That is the brake pressure accumulator pump, which is used to provide pressure for the power brakes. The Prius can't use engine vacuum like ordinary cars, since the engine does not run continuously. An intermittent ratcheting sound while braking is normal. The Prius runs this pump when you open the driver's door on a Gen III, in anticipation of needing the brakes.

    Tom
     
    #16 qbee42, Oct 25, 2011
  17. PaJa

    PaJa Senior member

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    The poster wrote about the pumping sound at every brake pedal hit. It is not standard, I suppose.
     
    #17 PaJa, Oct 31, 2011
  18. qbee42

    qbee42 My other car is a boat

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    The pump should run about every third time you brake. Obviously that isn't a hard number, since brake application varies by need, but the accumulator pump does not run every time you press the brakes.

    Tom
     
    #18 qbee42, Oct 31, 2011
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