Brake pedal won't depress

Discussion in 'Prime Main Forum (2017-Current)' started by btrflies, Oct 8, 2017.

  1. taka05black

    taka05black Junior Member

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    Good to know such warning exists, thanks!
    Of course I meant the pump sound I am familiar with for a decade.
     
  2. btrflies

    btrflies Junior Member

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    Ugh, tonight a new horrible sound has started while braking. I didn't notice it until I was backing into the garage. It's a loud eeeerrrrmmmm sound. I have a video but unfortunately this won't allow me to upload it. I keep hearing about the orchestra of sounds the Prime makes, but this just doesn't sound right. Guess it's time to bring it back to the dealership

    One more note, I just replicated the stiff brake upon starting problem. I opened the driver door, got in, shut the door, sat in the car for 10 minutes without touching the brake. Then after that 10 minutes I pressed the brake and it was rock solid. Took my foot off the brake, pressed my foot back on the brake a second time and it pressed down easily like normal. So there it is. But the question now is....is that normal? Or does that point to a problem with the car? Especially now that it is making a terrible noise when braking.
     
    #22 btrflies, Oct 11, 2017
    Last edited: Oct 11, 2017
  3. bwilson4web

    bwilson4web i3 and Prime

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    Just make clear, no attempt to start the car during this test?
    Then you could start the car?

    Now that there is a way to replicate the problem and while it is under warranty, time to find out:
    Bob Wilson
     
    #23 bwilson4web, Oct 11, 2017
    Last edited: Oct 11, 2017
  4. bwilson4web

    bwilson4web i3 and Prime

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  5. taka05black

    taka05black Junior Member

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    That's scary... Sorry to hear that. I'm curious to know if stiff brake thing is correlated to the problem...
     
  6. btrflies

    btrflies Junior Member

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    I just replicated again, sitting in car for 5 minutes before touching anything...then this time after 5 minutes, I put my foot on the brake (it was hard again) and while my foot was pressing down on the hard unresponsive brake, I hit the power button and the car did power on and was ready to drive. And as soon as I did hit the power button, with my foot on the hard break, I could feel the brake nudge/clunk down and depress like normal. But there was a little quick nudge as it first sort of popped down into place. So this problem doesn't affect the readiness of the car to drive. So is this just normal for this car? Or does it point to a further problem (because I'm now hearing a new weird braking sound while moving). I'd be curious to know if everyone else with a Prius Prime can replicate this and have the same thing happens to them all. Anyone out there want to try and let me know?
     
  7. bisco

    bisco cookie crumbler

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    that's your pedestrian warning system.
     
  8. jaqueh

    jaqueh Active Member

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    Yes this is the same for me, but isn’t a problem when I’m driving.

    On the other hand. I do think that the brake pedal “feel” in this car is terrible. You can’t tell when friction brakes are engaging vs regen. And the brake assist is just as annoying in this car as it was with the gen 2. It almost makes it feel as if there are two brake systems. One that is extremely aggressive if you press the brake pedal slightly quicker than normal. And the other normal pedal feel is really slow and numb.
     
  9. btrflies

    btrflies Junior Member

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    OMG, I am an idiot! It IS the sound of pedestrian warning system! I thought that could be a possibility before but didn't think so because I had never heard it before. But I just looked on YouTube for videos of the sound and that is definitely it. I'm so sorry for wasting everyone's time! Thank you so much for everyone's help. Because of the initial brake problem (which turns out it doesn't really seem to be a problem...it's only when you don't immediately power on the car after entering) I think I got all hypersensitive to all and any noise emitting from the car while I was braking. Here's a link to one of the videos that lets you hear the pedestrian warning system, along with other normal sounds. Again, I am so sorry to all of you but I'm so thankful to everyone one of you who took the time to help me

     
  10. Prodigyplace

    Prodigyplace Senior Member

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    You know repairs can be expensive and this complex car is a huge unknown.
    We understand and realize education takes time.
     
  11. taka05black

    taka05black Junior Member

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    I'm feeling better now, too! I usually try to avoid becoming an early tester, but I couldn't wait for another year this time.
    So your problem could be my problem.

    Happy driving!
     
  12. MikeDee

    MikeDee Senior Member

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    I think this is normal and I’m pretty sure my car behaves the same way. Drive any car with power brakes. When the car is off, the pedal is hard and high. When you start the car and the vacuum boost kicks in, the pedal lowers and becomes softer.
     
  13. Prodigyplace

    Prodigyplace Senior Member

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    The Prius does not use engine vacuum boost though.
     
  14. MikeDee

    MikeDee Senior Member

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    As I understand it, it has a electric vacuum (or pressure maybe) accumulator. Basically functions the same in that it provides power boost to the brakes. No electric power, no boost.


    iPhone ? Pro
     
  15. ChapmanF

    ChapmanF Senior Member

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    It's already been explained before, though, not just elsewhere on PriusChat, but at least twice above in this thread: the pressure accumulator, when topped off by the electric pump, normally holds usable pressure for many hours, or for about 30 strokes of the brake pedal, which is what you normally need in a Gen 1 or Gen 3 Prius after shutting the power off, before the pedal becomes hard. (Gen 2 worked a different way.) Usually you can exhaust the vacuum in a conventional car's power brakes in 2 or 3 strokes if the engine's not running.

    There seems to be one open question whether Gen 4 or Prime may have added an extra valve that blocks off the boost pressure when "asleep", which will eventually get answered yes or no by someone with an active techinfo subscription. But otherwise, the norm for the Prius is that the boost remains usable for a good long time.

    -Chap
     
  16. bisco

    bisco cookie crumbler

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    pleasure.
     
  17. Glamma5

    Glamma5 New Member

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    I have been having the same issue with my 2018 Corolla. The brake wont depress and the car won't start. I have push button start. This has happened 3 times. Dealership cant reproduce the problem so they dont know what is happening. This last time is when I actually realized that when the car won't start the brake pedal is not depressing so hopefully they will be able to determine the culprit and fix it. Wish me luck. She is at dealership as we speak.
     
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  18. bisco

    bisco cookie crumbler

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    all the best!(y)
     
  19. m8547

    m8547 Active Member

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    If it's the same problem as in the Prime, to reproduce the problem try sitting in the car for a few minutes without starting it or touching the brake or anything. The brake pedal should feel hard after that if it's the same issue people here are having.

    To fix it, try getting out and getting back in. Getting in (Specifically, I think opening the driver's door) triggers the brake pump in the Prime. You might hear a slight buzzing or humming if it's running.

    It should still be possible to start the car by pressing hard on the brake. Put some weight into it, you won't damage anything. Once it starts the brake pump should run and the pedal will immediately become normal.

    I always assumed this problem was weirdness caused by the fact that we have regen braking. But maybe it's more related to the fact that these cars can automatically control the brakes for dynamic cruise control. Or maybe it's a defect?
     
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