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Brake noise on depression and release, with audio

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by peteandbeans, Apr 25, 2023.

  1. peteandbeans

    peteandbeans New Member

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    Hey all, I did a brake booster not long ago on my 2012 two, using the TSB part no. and techstream to bleed. I noticed the new brake booster makes this noises like it's pushing air back and forth or pushing it out then sucking it in or maybe that it always made this noise and it is normal? To be clear I'm not referring to the pump running, but the air noise most clear as I release at the end. From what I can figure out it's either normal, air left in the brake system that needs to be bled(I've done it several times now and I have all of my pedal.) or the push rod is leaking air? I think it's normal because I believe I can hear it in the nutzaboutbolts video where he does the brake bleeding procedure without a scan tool but it's not clear. Anyone else get this? Am I crazy?
     
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  2. peteandbeans

    peteandbeans New Member

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    Okay this is to hit the minimum post requirements.
     
  3. bisco

    bisco cookie crumbler

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    not getting the video
     
  4. ChapmanF

    ChapmanF Senior Member

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    If I remember right, not so very long ago, the PriusChat media gallery wouldn't even let a video be uploaded.

    So I'm thinking, the ability to upload a video, even if it doesn't quite exactly play yet, could be a sign of progress?
     
  5. peteandbeans

    peteandbeans New Member

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    I am sorry for the delay, it appears I need *more than* 4 posts to post a link, will update with link as soon as I can
     
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  6. peteandbeans

    peteandbeans New Member

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    Hello I have returned with a link https://youtube.com/shorts/0MbI-hmcBto?feature=share
    Can't for the life of me remember if that's always how it was, the little puff when I press in and that little suck noise as it returns, if I press it real slow sometimes it doesn't or maybe it's quieter? Those things are pricey hope I don't need a new one again
     
  7. ChapmanF

    ChapmanF Senior Member

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    Without watching your video at the moment, from your description of the sounds I suspect bubbles in the system. In a conventional car, you would feel a spongy low brake pedal, because you're squeezing the bubbles. You don't feel that in a Prius, because the computer just shoots more pressurized fluid into the brake lines until the bubbles are squeezed and the pressure is right, but you hear an extra little whoosh from it doing that. Then when you release the brakes, the bubbles expand again and drive that extra fluid back to the reservoir, and you hear that little whoosh too.

    The Prius brake system has a magical way for bubbles to slowly appear in it over time even when no one ever did any work that let air in. You can read about it here.

    The long-form "there might be bubbles in the head end" brake bleed procedure can get those out. You may eventually have to do it again, and you may eventually have to replace the actuator. But if the only bubbles so far have come from a very slow leak, then there may be quite a while before you have to repeat the process.

    If it doesn't take quite a while, then the time to replace the actuator may have come.

    I definitely would try to bleed the bubbles out, the sooner the better. There are rare but occasional reports here of people experiencing floored-pedal-no-stoppie brake failures (much more rare than the usual "I had to stomp really hard but it stopped" kind, which aren't as awful). My unproven theory for those is that there were bubbles in the line, probably there for a while, normally not very noticeable except for the whoosh sounds, but then something else happened that triggered the brakes to the fail-safe pedal-powered mode, and then the bubbles were too big for the pedal to squeeze the brakes. (In other words, with big enough bubbles, the "fail-safe" mode may not really be safe.)
     
  8. peteandbeans

    peteandbeans New Member

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    Ugh I just spent 1300 to replace the damn thing. You're saying I might need a new one again? The long form bleed didn't help before but I could be missing something there. Not excited to get ripped off at the stealership for a 30 minute brake bleed job but seems like the only option. Sounds like the new booster isn't any more reliable than the old one from what you're saying. I really should have just bought a Corolla and not dealt with this crap.
     
  9. peteandbeans

    peteandbeans New Member

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    Think it's the ends of the road for this thing with me
     
  10. rjparker

    rjparker Tu Humilde Sirviente

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    You are right about that.

    It is highly unlikely you need another new master cylinder/brake booster. Without Techstream or an XTool D8, you don't bleed everything in the current brake booster. Let Toyota do it for an hours labor especially since you are in for $1300 already.