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Dash Noise, Not Vibration?

Discussion in 'Gen 2 Prius Technical Discussion' started by mpg9999, Sep 22, 2012.

  1. mpg9999

    mpg9999 Junior Member

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    My girlfriend just picked up a 2007 Prius Touring, 78,000 miles, original owner. It was a private sale and I took a look at it for her. I'm just learning about the Prius and stuff to look for, but everything looked good on it to me. After purchasing it she noticed a noise coming from the drivers side dash. I searched here and saw that dash rattles are common, but this sounds more like an electric buzzing/whirring noise. The duration of the noise is always about 2 to 3 seconds in length, then it stops. There doesn't seem to be any common factor for when it occurs. Is there anything electric on the drives side dash (far left side, closest to the window), that might be making this noise? It's not super loud, you can't hear it if the radio is on.
     
    #1 mpg9999, Sep 22, 2012
  2. PriusGuy32

    PriusGuy32 Prius Driver Extraordinaire

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    Does it occur all of the time or when you are turning the car on or off?

    Sounds to me like a pump. Ive read that the brakes are assisted by a pump that makes strange noises when your foot is on it. Also, the inverter coolant pump Im pretty sure is under the hood in front of the drivers side but towards the front of the car. When they start to go bad they get noisy.
     
    #2 PriusGuy32, Sep 23, 2012
  3. mpg9999

    mpg9999 Junior Member

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    It doesn't make the noise constantly, but it's not only when hitting the brakes, or only when turning the car on or off. It did seem to happen more often while braking, but it's definitely happened while not braking as well. It may just be it's more noticeable when you are coming to a stop because it's quieter. Can't narrow it down to any one situation. I had already checked to make sure the coolant pump was working by doing this
     
    #3 mpg9999, Sep 23, 2012
  4. edthefox5

    edthefox5 Senior Member

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    Thats the brake vacuum motor. Since you need vacuum from the engine for the brakes the problem is the engine doesn't run all the time so they needed an assist motor to make sure there's always sufficient vac all the time. When you step on the brakes it uses vacuum so the motor turns on to fulfill that request.
    Sounds like a rattle snake right? Just push the brakes a few times and you'll hear it come on. Thats really the only electric motor you can clearly hear from the cabin. Its right behind the drivers dash.
     
    #4 edthefox5, Sep 23, 2012
  5. mpg9999

    mpg9999 Junior Member

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    Thanks! That sounds like it's probably it. It mostly happens when hitting the brakes, but not all the time. Will the vacuum motor turn on when the brakes aren't applied if the vacuum is too low? Good to know that it's probably not an issue.
     
    #5 mpg9999, Sep 23, 2012
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