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Rear brakes lock up as soon as car is started

Discussion in 'Gen 4 Prius Technical Discussion' started by JStrenk, Jul 8, 2023.

  1. JStrenk

    JStrenk Active Member

    Joined:
    Nov 29, 2011
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    Location:
    Ravenna
    Vehicle:
    2016 Prius
    Model:
    Two
    Just replaced the rear pads on my 2016 and the rear wheels turn freely but as soon as I start the car, I hear a buzzing noise and the rear wheels lock up. As soon as I turn the power off, the wheels turn freely. Start the car again and within a couple of seconds, the rear wheels lock up again.

    It not a total lockup, but I can’t turn it by hand, I need a bar to turn it.

    just a quick trip down the road turned the new rotor blue.

    I did make sure the slot in the caliper piston slot was aligned properly, brake pads move smoothly in the guides and caliper moves freely on the pins.
     
    #1 JStrenk, Jul 8, 2023
  2. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
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    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    The buzzing noise in the front is a small pump that builds up brake fluid pressure, but the pressure is only to be stored in an accumulator until the brake system opens valves to apply the pressure to the brakes.

    If the pumping-up of accumulator pressure is being accompanied immediately by pressure at rear brakes, without any use of the pedal, I would suspect some valve(s) in the actuator not closing tightly.
     
    #2 ChapmanF, Jul 8, 2023
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