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Prius Prime makes a clicking noise when coming to a stop. Can anyone check theirs to see if normal?

Discussion in 'Prime Main Forum (2017-2022)' started by Cfrea, Apr 24, 2017.

  1. Cfrea

    Cfrea Junior Member

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    On my new Prime I have some clicking noises that come from the driver side under the steering wheel when coming to a stop.

    It only happens when applying the brakes. The best way to test is the following, be in EV mode, drive on a quiet road with A/C and radio off. Come to a complete stop and continue to hold the brakes down. At this point I will hear a small ticking noise like 3-5 times then it disappears (like tick-tick-------tick---tick). This happens each and every time the car comes to a stop and is really only noticeable on a quiet street not on a major road where there is a lot of road noise.

    Can any of you please try this and let me know if you experience this sound? Or if anyone is in the SoCal LA area would love to meet and compare. Thank you!
     
    bisco likes this.
  2. mr88cet

    mr88cet Senior Member

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    Does it sound somewhat like a "vibraslap" (
    That's what it sounds like on my Gen-2 at least.

    If so, I was wondering whether the P.Prime would have that sound too...

    I'll tell you what I *think* it is, but I'm not 100% sure: I think it's a vacuum pump pumping down a vacuum reservoir that powers the brakes.

    Almost all cars use ICE intake vacuum to power brakes. Diesel cars always have a wide-open throttle, so their would-be intake vacuum becomes more of a vague suction. They therefore add a mechanical vacuum pump, so that, as long as the engine is turning, it generates a vacuum.

    The Prius, of course often intentionally turns off the engine entirely. It appears that what it does is seal off the vacuum system when they turn off the engine, leaving a vacuum reservoir the brake system sucks against. When that vacuum amount bleeds down a bit, it sucks it down further with a vacuum pump, which I believe is what's making that sound.

    That then is why, at least by my theory, on my Gen-2, I can sometimes, while the engine is off, seemingly lightly tap the brakes, but instead get almost a "banging" hard application of the brakes: the vacuum reservoir is ... full (meaning empty), so even a slight application of the brakes produces a sudden bang of brake force.


    iPhone ? Pro
     
  3. Cfrea

    Cfrea Junior Member

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    No its that distinctive 'pump' noise you hear but more like a little clicking noise
     
  4. jburke313

    jburke313 Member

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    Mine does not make this clicking sound.
     
  5. huskers

    huskers Senior Member

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    I have no clicking as well.
     
  6. Samprocat

    Samprocat Active Member

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    I have not discovered this..on my Prime or my wife....
    I do have noise for couple second after car is seating for couple hours and you turn the ignition on in READY ....
    What is normal what owners manual describes
    In my opinion is best way to test with hood open and have someone else do this for you while you looking at the engine bay to see where is this noise coming from

    Posted via the PriusChat mobile app.
     
    priuscatprimeguy likes this.
  7. Cfrea

    Cfrea Junior Member

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    Here is the sound I'm talking about:



    I tested this by simply turning on the car in my driveway and hitting the brakes, after a second of holding down the brakes the sound you hear happens.
     
  8. bhtooefr

    bhtooefr Senior Member

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    I hear it in my Gen 4 sometimes when braking. Sounds a lot like when the ABS pump would be working in a previous car, and I'd guess that's exactly what's going on - it's modulating fluid pressure in the braking system to ensure consistent braking performance at the same pedal pressure.

    Remember, the Prius has a weird braking system, in which it simulates brake feel to try (emphasis on try) to make things consistent between regenerative and friction braking.
     
  9. Cfrea

    Cfrea Junior Member

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    You hear a pump sound or the sound depicted in the video? The sound in the video is more electrical whereas the sound you may be referring to is a pump of some sort
     
  10. bhtooefr

    bhtooefr Senior Member

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    I'm hearing a clicking sound, which is almost certainly the solenoids in the braking system functioning to modulate fluid pressure. This is in addition to occasional pump sounds.
     
  11. JustCharles

    JustCharles New Member

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  12. Rickyedger

    Rickyedger Junior Member

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    Did you ever find out what the noise was? My gen 4 prius is making it and there taking it into the shop next week. We think it might be the driver side axle

    Posted via the PriusChat mobile app.