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Breaks - something aint right

Discussion in 'Prime Care, Maintenance and Troubleshooting' started by Skapruisprime, Feb 17, 2018.

  1. Skapruisprime

    Skapruisprime Member

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    Had the PP for a week with 350 miles, I think Im having some brake issues but Im not sure if this is normal for a hybrid/EV.

    There’s very little pedal feel and coming to a stop, its very jerky and has some mechanical grind. The worst is when Im reversing (with brakes), its like Im stepping on air...no feel at all for the first two inches into tye pedal.

    Im thinking it needs brake fluid bleed/flush??
     
  2. bisco

    bisco cookie crumbler

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    unlikely in a new car. more likely, you're just not familiar. why not call your salesperson and ask to test drive another, prius brakes are funky.
    the grinding may be rust that accumulates on the rotors from condensation. you can clean them up each drive by putting her in neutral for a minute, this allows for friction braking only.
     
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  3. Mendel Leisk

    Mendel Leisk Senior Member

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    I would contact the dealership, that's practically fresh off the boat, I'd bet it would be a freeby, a mechanic could take it around the block, see what he thinks.
     
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  4. Skapruisprime

    Skapruisprime Member

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    Maybe I do need to get use to it, my previous cars have great pedal feel so it could be that
     
  5. fotomoto

    fotomoto Senior Member

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    Maybe it's because you're expecting a break to brake? :confused: . :)

    :coffee:

    Very common issue for hybrids when backing out of a garage first thing in the morning. This is due to the low to light use of the friction brakes when they are cold and grabby and the sound is due to the surface buildup of rust on the cast-iron surface of the brake rotors. A more forceful application of the brake pedal will warm up the rotors, scrub off the light surface rust, and return the friction part of the braking action to a more normal feel/reaction.

    This can also be weather related as cool, moist conditions (especially overnight) lead to more surface rust and colder rotors in general.

    You'll eventually learn new muscle memory and not think as much about it.
     
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    I do not know, "mechanical grind" doesn't sound good. Ditto for "jerky" and "no feel in reverse". It may be ok, but the car's brand new, and all-in-all? I would trust your hunches, better safe than sorry.

    I got a car back after a brake fluid replacement, and it turned out one rear brake was not engaging at all. I wasn't that familiar with the car, wrote it off as unfamiliar brakes, but started finding more and more weird stuff. It was only after picking up our son and daughter in law (it was their car) that it finally came to a head: my son got behind the wheel, drove a few feet touched the brakes and it was "what is wrong with the brakes".

    Yeah: phone up service, see if a mechanic can test drive it. It's 5~10 minutes for them, hopefully figure it out, one way or the other.
     
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  7. padroo

    padroo Senior Member

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    My 2008 Prius had that grind all the time but I have not noticed it on my new Gen 4. I don't know if maybe they are using a different brake rotor than earlier Prii or it just hasn't happened yet. My car sets for 3 and 4 days at a time and if it was going to rust up especially this time of year you would think it would have happened by now.

    I agree with Mendel, take it back to the dealer, better safe than sorry.
     
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  8. Skapruisprime

    Skapruisprime Member

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    Its def not rust rotors as I garage and know what rust/moist rotors are
     
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  9. bisco

    bisco cookie crumbler

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    mine rust in my garage. keep in mind, prius brakes are built on tranny regen/caliper combo. they won't feel like anything you have driven before, unless you've driven hybrids.
     
  10. Wuzki

    Wuzki Member

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    Our break system is build as an simulator. Just like a joystick of a video game. Computer is making decisions of physical break or magnetic break. It’s a very annoying thing of the hv.
     
  11. jaqueh

    jaqueh Active Member

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    This is only partially true. The pedals are very much hydraulic and connected to the physical brakes when reversing and traveling at low speeds.
     
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  12. ChapmanF

    ChapmanF Senior Member

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    Unless it has changed for Gen 4 / Prime, the very much hydraulic pedal is connected to a "stroke simulator", a spring-loaded chamber that mimics the feel of physical brakes. Meanwhile, a pressure sensor and a stroke sensor inform the computer of your pedal movement and pressure, and the computer drives the valves in the actuator to send fluid from a pumped-up pressure accumulator out to the physical brakes. This is true even in reverse and at low speeds.

    Only in the case of an actual electrical or computer failure will the switching valves in the actuator fall into their fail-safe position, where the pedal directly acts on the front brakes, and nothing acts on the rear.

    That basic description is true for sure of Gen 1, 2, and 3, though some details did change between 1 and 2, and others between 2 and 3. I have not studied the Gen 4 New Car Features manual, to be sure of what details might have changed since Gen 3, but if the basic description I've given here is off, surely somebody who has studied it will post an excerpt to set me straight.

    -Chap
     
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  13. bisco

    bisco cookie crumbler

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    i find them a bit different than regular brakes, but even on my first prius test drive, it never occurred to me that something could be wrong with them.
     
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  14. Elektroingenieur

    Elektroingenieur Senior Member

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    For the fourth generation, fail-safe braking during a power supply malfunction or brake actuator failure works on all four wheel cylinders; otherwise, your summary is correct.
     
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  15. The Electric Me

    The Electric Me Go Speed Go!

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    I'm just going to default to the advice that if you at all aren't sure or comfortable about your brakes?
    Go get them checked out.
    I would go to the dealership and ask if I could test drive a similar Prius to compare feel. Have them check the system. Brakes are obviously a safety issue. Brakes are just something I don't speculate about. If they don't feel right to you? You owe it to yourself to have them checked out.
     
  16. Skapruisprime

    Skapruisprime Member

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    Brakes work, just very different that the regular hydraulic brakes.

    I guess Im just not use to it yet.

    I have been spoiled with 4 piston fronts and 2 piston rear brembos on my last two cars haha
     
  17. Mendel Leisk

    Mendel Leisk Senior Member

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    I find the feel very natural, at least on our third gen.
     
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  18. HPrimeAdvanced

    HPrimeAdvanced Senior Member

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    The brakes on my Prime feel "different" than some other cars I've driven, but they don't grind, and pedal response feels natural to me. Of course, I'm in temperate Socal, so your extreme weather in Massachusetts is something I've never experienced with my hybrids. In your position, I would definitely have the dealer mechanic go drive the car with you to resolve this PROBLEM (I hate to call these things Issues; they are PROBLEMS!).
    By the way, Congratulations on your new Prime and hoping for a quick resolution!


    Posted via the PriusChat mobile app.
    AChoiredTaste.com
     
  19. jaqueh

    jaqueh Active Member

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    Yeah the brakes on my gen 2 are very much simulated. Same brake feel no matter the condition, but I feel like Toyota changed something because of the constant brake feel complaints. This never happened on my gen 2.
     
    #19 jaqueh, Feb 25, 2018
    Last edited: Feb 25, 2018
  20. jerrymildred

    jerrymildred Senior Member

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    Prius brakes are different. Mine are great. But if they feel weird to you, I'd recommend at least driving another one to compare or else asking the dealer to check them out. They may be just fine, but then again, the only thing a car absolutely has to do without fail is to stop.
     
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