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Newbie question: brake pedal noise?

Discussion in 'Gen 3 Prius Technical Discussion' started by FlyboyZR1, May 31, 2014.

  1. FlyboyZR1

    FlyboyZR1 New Member

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    I recently purchased a 2014 Prius with the package 5 trim. I'm completely loving the car, but noticed when stepping on the brake pedal I hear a soft "swoosh" noise from under the dash. Almost like a short vacuum or sucking sound.

    The car has 500 miles, and I don't recall hearing that noise initially.

    Is this normal, or something I should have the dealer look at?
     
  2. spiderman

    spiderman wretched

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    Sounds familiar. But you can always take it in of it makes you feel better.
     
  3. Former Member 68813

    Former Member 68813 Senior Member

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    I hear that when I suddenly press the pedal hard. None of that with the usual brake modulation. No idea what that is as the brakes should be hydraulic and not air assisted. There is a compressed nitrogen compartment, but it shouldn't be near the brake pedal IMHO.
     
  4. JC91006

    JC91006 Senior Member

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    If the car sounds like a space ship when coming to a stop, then it's normal

    SM-N900P ?
     
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  5. Former Member 68813

    Former Member 68813 Senior Member

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    No, we are not talking about the usual hydraulic pump action, but rather compressed air release like sound.
     
  6. FlyboyZR1

    FlyboyZR1 New Member

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    Yes the sound seems to happen every time I step on the brake. It's kind of annoying every time I step on the brake to hear "pssssst". It's coming from somewhere under the dash in the center of the car. The first few hundred miles driving the car it never made that noise, so I'll probably take it in to the dealer.
     
  7. Prius-Paul

    Prius-Paul New Member

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    i was wondering the same think....can someone chime in and school us on this?!!
     
  8. FlyboyZR1

    FlyboyZR1 New Member

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    The noise is normal ... I drove another new Prius that does it too. I'm not sure of the exact explanation why, but they said all Toyota's will eventually make the noise with the new braking systems.
     
  9. Stratman

    Stratman Member

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    I too have recently noticed that same sort of hissing sound and mine is new also. It's not noticeable till I've almost come to a complete stop and it's not generated by the pads.
     
  10. ramattos

    ramattos Junior Member

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    most likely it is just the stroke simulator, my '10 does the same thing.
     
  11. GregP507

    GregP507 Senior Member

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    Sounds like the rubber boot that protects the brake plunger is being compressed, and air is escaping from the inside. I suppose someone could try to open a wider vent-hole if it's really a problem.
     
  12. Grren4ever

    Grren4ever Active Member

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    I have had my 2013 prius for almost a year now and I notice that sound once in a while. One time a soccer ball rolled across the street and I slammed on the brakes and I heard a fart noise coming from probably the master cylinder. Felt it on the foot pedal too. The GF swears it wasn't her farting so must be the car!

    Get this - in the winter when it is near freezing, the master cylinder makes even a louder fart noise a few minutes after I power off the car. Even my best buddy who is the master tech at a Toyota dealership can't give me a direct answer.
     
  13. retired4999

    retired4999 Prius driver since 2005

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    I think it's the brake acuator making that barking noise.
     
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  14. A617

    A617 Member

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    That swoosh sound is indicator of a good working accumulator , an accumulator its spherical ball that has a bladder split horizontally, one side has Nitrogen gas the other side has brake fluid, its function is to act like a brake booster to reduce brake pedal effort so you can stop your car without pumping your brakes several time, since our engine cuts off its is not applicable to have a conventional vacuum brake booster, so in place it has an electric pump and an accumulator, the electric pump takes the brake fluid and stores into the accumulator as more brake fluid enters the accumulator the nitrogen side of the accumulator begins to compress until a specific pressure is reached then the pump cuts off and its now ready for the next brake application, when you hit your brakes the pressure that was build up in the accumulator by the electric pump is released into the brake master cylinder to decrease brake pedal effort and when it dose that it makes a swoosh releasing the pressure that was stored up and sending it into the brake master cylinder then to the abs module and to the brakes.

    That's about it folks!
     
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  15. house2013

    house2013 Junior Member

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    A617 thanks for the explanation
     
  16. Former Member 68813

    Former Member 68813 Senior Member

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    Good story, but like I said in my above post that air sound should be audible in engine compartment and not brake pedal well.
     
  17. Mendel Leisk

    Mendel Leisk Senior Member

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    Never heard that. Do hear the regen whine.