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Before starting the engine, it makes a noise

Discussion in 'Gen 3 Prius Main Forum' started by priusenvious1, Jan 3, 2013.

  1. priusenvious1

    priusenvious1 Member

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    2012 Prius Plug-in
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    Plug-in Advanced
    The noise seems routine. It happens when you get close to the car and open your door. I guess the car is anticipating that you will start the car soon and under the hood, some subtle mechanical noises occur. Just wondering what that noise is?
     
    #1 priusenvious1, Jan 3, 2013
  2. fotomoto

    fotomoto Senior Member

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    It's the hybrid brakes doing a self-check/priming of the system; quite normal nothing to worry about.
     
    #2 fotomoto, Jan 3, 2013
    pichner likes this.
  3. priusenvious1

    priusenvious1 Member

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    Wow, that's cool.
     
    #3 priusenvious1, Jan 3, 2013
  4. Sergio-PL

    Sergio-PL Member

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    It's a vacuum pump that prepares brakes to be instant-ready to do their job. It happens allways, when you unlock the car and open driver-side doors.

    Then, when you hit "POWER" to get car to "READY" state, it does computers boot-up, short self-check and then you can hear relay clicks from the boot. They engage HV battery and car goes to READY state. Your are ready to take off.

    The sound you describe can be heard also on traffic jams. After 2 - 3 stops it recreates vacuum and you can hear exact same noise. It happens all the time while you drive and more vacuum is needed. Sorry if you will now start to hear it all the time :rolleyes:

    When you park, turn off the car and leave it for about 5 hours it will do a fuel system check and make sound like some kind of engine working.

    Prius is full of wierd sounds. Most of the time they are normal :cool:
     
    #4 Sergio-PL, Jan 3, 2013
    priusenvious1 and Direwulff like this.
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