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Feels like loss of brake power?

Discussion in 'Gen 2 Prius Main Forum' started by DangNabbit, Jun 13, 2018.

  1. DangNabbit

    DangNabbit Junior Member

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    I also would like to see if others have had this issue....

    In the past 2 months I’ve had the Prius, it feels like it has lost braking power/ability 2-3 times. The first time it happened I thought it slipped on the painted pavement during the rain but there wasn’t any traction lights.

    It just occurred again yesterday. As I was stopping the vehicle felt like it lost the brakes. This time the road conditions were dry and still no traction light flashing.

    I do remember hearing the engine or something sounding like it was reving up as I was trying to come to a stop. Sounded like a vroom vroom with a little bit of pulse coming from the brake pedal

    I am worried that it’s the brake actuator... the vehicle didn’t get the recall done and now it’s too late. I don’t see any warning signs but the vehicle does have the barking noise problem

    #1A moment ago
     
    #1 DangNabbit, Jun 13, 2018
  2. bisco

    bisco cookie crumbler

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    at what speeds does it happen?
     
    #2 bisco, Jun 13, 2018
  3. DangNabbit

    DangNabbit Junior Member

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    Can’t say for sure, but I think it’s usally 30 mph or lower when I’m trying to come to a complete stop.
     
    #3 DangNabbit, Jun 14, 2018
  4. bisco

    bisco cookie crumbler

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    there is a transition from regen to friction braking around 6mph iirc. some feel it as a loss of braking because of the change in 'feel', almost as if the car is slipping or lurching, and requires more pressure on the brake pedal.
     
    #4 bisco, Jun 14, 2018
  5. DangNabbit

    DangNabbit Junior Member

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    Had it happen again today coming to a stop light. As I was applying more pressure the engine sounded like it was reving higher.

    I only had 2 bars of battery on the MFD.
     
    #5 DangNabbit, Jun 14, 2018
  6. bisco

    bisco cookie crumbler

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    what speed?
     
    #6 bisco, Jun 14, 2018
  7. DangNabbit

    DangNabbit Junior Member

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    This time was less than 10mph. Closer to 0.
    The harder I pressed the brake, the more the engine sounded like it was reving
     
    #7 DangNabbit, Jun 14, 2018
  8. bisco

    bisco cookie crumbler

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    that doesn't sound good, how many miles on her?
     
    #8 bisco, Jun 14, 2018
  9. DangNabbit

    DangNabbit Junior Member

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    Just sightly over 127,000. Anything that might be remotely causing this issue?
     
    #9 DangNabbit, Jun 14, 2018
  10. bisco

    bisco cookie crumbler

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    i'm stumped. maybe check for trouble codes just in case.
     
    #10 bisco, Jun 14, 2018
  11. ITBland

    ITBland Active Member

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    This is just a theory: You suspect a bad traction battery AND you sure sound like you have the brake actuator failing. So, If the battery is too low to provide much power to the system AND the brake actuator is working harder than normal and calling for more power, the engine needs to rev to generate all the power that the failing brake actuator thinks it needs to stop the car.
    Off to look at the wiring diagram to see if the brake actuator uses the traction battery or the 12v...
    EDIT: It is 12v only, BUT has 2 10A fuses, a 25A fuse and a 30A fuse, so potentially a lot of 12v power could be called by the ABS system--keeping with my theory, try putting the MFD into maintenance mode, signal check and then stomp hard (and fast) on the brake pedal (and hold it) and see if the voltage drops. You should not need to be moving to try this (you won't be paying attention to driving if watching the voltage on the MFD) the ABS should respond to the brake pedal action. (Actually, it might not--ABS does watch the speed, too. Maybe get someone to watch the voltage and try a hard stop.)
    As an aside, you're sure it's the ICE making the noise, not the actuator running like mad?
    Oh, and as bisco said, can you read the ABS codes? (TechStream can, but some cheapie readers can't access all of the buses-TechStream will tell you at startup if not all buses are available.)
     
    #11 ITBland, Jun 14, 2018
    Last edited: Jun 14, 2018
  12. PAUL SCHULTZ

    PAUL SCHULTZ Member

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    Is your floor mat propely in place? Could it be catching/binding on the brake and/or accelerator pedals??
     
    #12 PAUL SCHULTZ, Jun 15, 2018
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