Very faint clicks at stop from brake actuator

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by howardc64, May 6, 2026 at 11:02 AM.

  1. howardc64

    howardc64 Member

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    Very faint clicks when at a stop from brake actuator. Had wife pull the car into drive way, gear in D, foot on brake, popped the hood and found this faint click (~1x/s) coming from brake actuator area. Quite difficult to pickup even in a quiet cabin.

    Brake works fine. Actuator pump seems to run at same duty cycle as it always has.

    Last brake fluid flush was probably > 10 years ago simply due to the complexity of flushing this system (have techstream and know the process)

    Actuator must have a high pressure accumulator of course. No idea how much pressure is maintained. Need to read up more. Currently spending accumulator diagnosing effort on an Audi DSG transmission which has a 400 PSI campbell soup can sized accumulator to drive its actuators and clutch packs haha.

    Anyone encountered before?
     
    #1 howardc64, May 6, 2026 at 11:02 AM
  2. PriusCamper

    PriusCamper Senior Member

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    If you don't hear clicks when you open the car door to drive it after not driving in a while you can hear accumulator pump powering up. If that's the case, keep searching for another source for the clicks.
     
    #2 PriusCamper, May 6, 2026 at 2:01 PM
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  3. howardc64

    howardc64 Member

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    Good idea, I'll check this more carefully. Familiar with Prius running accumulator pump when first open the driver door in garage. I don't recall the faint clicks but will check carefully.

    I guess maybe an additional test... Run the car to get engine tranny hot. Park, wait awhile, open the door to trigger accumulator pump, see if click occur in case related to a hotter engine compartment
     
    #3 howardc64, May 6, 2026 at 2:12 PM
  4. ChapmanF

    ChapmanF Senior Member

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    The release valve for one of the brake lines could be leaking slightly, so that the apply valve for that same line has to repeatedly, briefly, click open to maintain the pressure in that line while you are holding the brake.

    What leaks through the release valve returns to the reservoir, and if you're there holding the brake long enough, the pump will eventually have to cycle again, but if the leak isn't big you might notice the clicking before noticing any drastic increase in the pump cycling.
     
    #4 ChapmanF, May 6, 2026 at 2:27 PM
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  5. howardc64

    howardc64 Member

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    Thanks! Will bring a stethoscope to the test and see if can pin point click to any brake lines can get access to.
     
    #5 howardc64, May 6, 2026 at 2:33 PM
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