Assist: brake sound check

Discussion in 'Prime Main Forum (2017-Current)' started by bb4srv, Nov 13, 2019.

  1. bb4srv

    bb4srv Member

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    Can the Prius Prime community help me. Every time I press the brake pedal, regardless of gear, I would hear the brake vacuum pump "whirring". The whirring sounds normal (not grinding) but this happens on every brake pedal press.

    Went to dealer and their tech said it's normal. They advised if there's any issue then there would be a CEL. My wife will be driving this car with our first 4 month old baby. So I want to be extra cautious. The car was in storage, and I don't recall the vacuum pump activating on every pedal press.

    So can anyone help me out and confirm you get the brake vacuum pump sound on every single brake press? Just put the car in P and press the brake. You should hear a little whirrr. Release and then repeat. See if the whirr happens again. Mine happens on every single press. Thank you.
     
    #1 bb4srv, Nov 13, 2019
    Last edited: Nov 13, 2019
  2. m8547

    m8547 Active Member

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    It's probably normal, but it depends on how hard you press the brakes. If you press lightly you might get 2-3 presses before the pump comes on. If you press firmly it might be every time. If you're driving and braking lightly so it's all regen, it might not come on at all or maybe only as you just come to a stop and the friction brakes activate. It will also come on when you open the driver's door to get in, and while you're driving if it hasn't been on for a while.

    Toyota has been using these electric brake booster systems since at least 2003, and they seem to be mostly very reliable. Hybrid braking has some quirks, but probably nothing that's actually dangerous.
     
  3. bb4srv

    bb4srv Member

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    At P is general pressure, not hard and press all the way down. It would whirr on every press. When in R, like backing into a spot, it would also whirr when I stop the creep. At D, slowing down I could sometime detect it too, but depending on road noise. But generally when in P, it would happen on every press using "normal" press.

    Yes, opening the driver door would also whirr, I know that part is normal operation.
     
  4. bisco

    bisco cookie crumbler

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    how long have you owned it, and for how many miles?

    have you noticed a change in frequency?
     
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  5. bb4srv

    bb4srv Member

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    It's 2018, with 13k miles. 90% EV.

    I haven't driven the car for the last 6 months but I don't recall the brake pump whirring on every press. Every so often yes, but not every press. But i'm not sure. want to check with community.
     
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  6. ChapmanF

    ChapmanF Senior Member

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    The car will complain if it thinks there's a problem. Short of that, it could be possible your focused attention is picking signs of an incipient problem, or it could be possible you're giving yourself something to worry about. How often the pump runs does depend on usage of the brakes. Is it staying pretty much quiet while you don't use the brakes at all?

    By the way, it's not a vacuum pump ... it pumps brake fluid, into a gas-filled can at a nice high (positive) pressure.
     
  7. bisco

    bisco cookie crumbler

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    has the 12 volt been sitting for 6 months?
     
  8. bb4srv

    bb4srv Member

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    12 v trickled charged during storage
     
    #8 bb4srv, Nov 13, 2019
    Last edited: Nov 13, 2019
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  9. bisco

    bisco cookie crumbler

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    hopefully, its just your imagination. maybe test drive another to see. without codes, there isn't much you can do.
     
  10. bb4srv

    bb4srv Member

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    Can anybody help and test if your brake pump whirrs on every brake press? Like press and after 1/2 second should hear the whirr. And repeat a few times to see if whirrs on every press.

    You can just do it in P. Quick test for me would be appreciated.
     
  11. Trollbait

    Trollbait It's a D&D thing

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    After not driving it for 6 months, it is possible the noise of normal operation just stands out to you more. Were you driving another hybrid during that time? If not, your brain could just be focusing on the differences from the last car you drove.
     
  12. m8547

    m8547 Active Member

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    I just tested it. If I press lightly, like I am planning on gently coming to a stop, the motor comes on every other time. If I press it moderately firmly, like a traffic light shortly ahead just turned yellow, it comes on every time. The majority of my stops use lighter pressure.

    If you're worried take it to the dealer and have them look at it. Then if anything were to happen you have documentation that you were concerned and they said it was ok.
     
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  13. bisco

    bisco cookie crumbler

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    can you post a video?
     
  14. Salamander_King

    Salamander_King Senior Member

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    PRIME makes so many weird sound not often heard in regular cars, but I got so usu to all those noises now I don't even know what "whirr" sound your are referring to. I am sure mine is making that noise too, but I don't specifically remember hearing any strange noise after pressing my brake. I will test it later today when I go home, and let you know.
     
  15. bisco

    bisco cookie crumbler

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    its the same sound as when you first open the drivers door
     
  16. Salamander_King

    Salamander_King Senior Member

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    OK I think I know what sound is like, but I can't remember ever hearing it when I apply brake. Not saying mine is not making the noise, but I just have not paid any attention to it to remember ever hearing similar sound to the one I hear when I open the door.
     
  17. PiPLosAngeles

    PiPLosAngeles Active Member

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    My 2018 has a different booster than my 2012. The 2018 booster stays engaged even after lifting your foot from the pedal until you start to go. It make starting on a steep hill nice, but it has the side effect that fine control of the brake is now impossible. Releasing the pedal ever so slightly to inch forward doesn't work.

    I don't hear the booster ever except when opening the driver door, and I'm the particular kind of person that would notice.
     
  18. Trollbait

    Trollbait It's a D&D thing

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    That's the hill start assist. It has nothing to do with the booster as it is on non-hybrids. With Toyota's system, it shouldn't engage if you don't depress the brake fully to the floor, or at least that is how it was on past models.
     
  19. PiPLosAngeles

    PiPLosAngeles Active Member

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    The brake system on my Prime does not resolve fine pedal movements. It seems like the pedal position sensor only has maybe 6 "levels" and you are braking at one of those 6 levels or not at all. It's most notable in a drive-though, where you might normally just lighten the pressure on the pedal to move forward a few feet in a normal car. The Prime can only do it in a jerky "release-grip-release" fashion.
     
  20. m8547

    m8547 Active Member

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    The grab and release is probably the electric motor shutting off when it thinks you're stopped, and turning back on when it thinks you want to go. It's not very smooth sometimes, but I don't think it's a problem with the braking system.
     
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