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Squeaking noise when brake pedal pressed, mostly at startup

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by ebee, Jan 23, 2022.

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  1. ebee

    ebee New Member

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    Hi all! Long time reader here (all the advice is so very appreciated - esp. the maintenance videos. Someday I'm going to attempt that EGR cleanout...) and first time poster.

    I've got a squeaking sound that seems to come from the brake pedal, occuring on startup on a 2013 Prius with just under 150k miles on the odometer. Here's a video, because a sound is worth a thousand words. It's a little worse/louder at the end of the video. Sorry for recording in the dark



    The sound you hear in the video happens most often when pressing the brake pedal when first starting the car. It's been happening more frequently over the past few months. I've always occasionally heard it when driving if I press hard on the brake pedal at a red light or something. The sound seems to come from down near the pedal itself, and doesn't seem to change if the door is open (as it is in the beginning of the video) or closed.

    Any ideas on what it might be? I'd appreciate any insight or educated guesses.
     
    #1 ebee, Jan 23, 2022
  2. ChapmanF

    ChapmanF Senior Member

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    That's no squeak, that's a honk. Sometimes we call it the bark, or the quack.

    It's hydraulic. Some brake fluid in the actuator is zipping through a nearly-shut valve and honking it like a saxophone reed.

    For the early Gen 3s, there was a firmware update to quack less. I had it done on my 2010. It quacked less. But I think the models starting in 2012 were supposed to have the updated firmware already. The service bulletin about it for 2010-11 was T-SB-0363-10, and they flashed my brake computer to version F152647108.

    The other thing that I kind of suspect contributes could be a gas bubble in the fluid. A person could try going through the Techstream "after actuator replacement" bleeding procedure, and see if that improves it some.
     
    #2 ChapmanF, Jan 24, 2022
    ebee likes this.
  3. ebee

    ebee New Member

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    Thank you for the correct terms to search for! No wonder I wasn't finding anything by searching. I'm now reading through those threads, and might try a brake bleed. I'm a little worried over whether it bodes ill for the state of the brake actuator/booster...

    Many thanks again for the very helpful information
     
    #3 ebee, Jan 25, 2022
  4. ChapmanF

    ChapmanF Senior Member

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    While nothing lasts forever, I'm pretty sure it was four or five years ago when I first noticed mine honking, and I went and had the anti-honk reflash done ('cause mine's a 2010), and played with the long-form bleed procedure. Nothing has failed since, so it seems like there can still be decent life remaining when the little things are taken care of.
     
    #4 ChapmanF, Jan 26, 2022
    ebee and Merkey like this.
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