Please help identify source of engine noise

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by batcat420, Dec 16, 2025.

  1. batcat420

    batcat420 Junior Member

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  2. Frontporch

    Frontporch Active Member

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    Its your brake booster pump. Seems louder than it needs to be. I can hear mine sitting in the driver seat. Always comes on when I open the driver's door and will cycle on again after using the brakes a little bit. Its normal. What is not normal is if it cycles on when you are not using the brakes. That is a pretty good indication that there is a leak

    I swapped out my master cylinder (accumulator?) and it definitely helped, but I have read of others that had the cycling going on for years.
     
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  3. PriusCamper

    PriusCamper Senior Member

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    Monitor how often you hear the noise... Once you hear it more than once in a minute its time for a brake booster pump swap.
     
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  4. bisco

    bisco cookie crumbler

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    houston, all systems normal
     
  5. indel

    indel Member

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    I normally hear this sounds whenever I am coming to a stop (using brakes of course) and it goes away as soon as I am fully stopped. Perhaps it's not the same sound, but I definitely do not get it when the vehicle is stationary, unless the car is not on and I open the driver's door.
     
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  6. batcat420

    batcat420 Junior Member

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    The noise is happening every 15 seconds or so now. Just ordered part number 47070-47060 (pump assembly, brake booster). Wish me luck!
     
  7. ASRDogman

    ASRDogman Senior Member

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    Mine has been cycling at 22 seconds for several years.....
     
  8. batcat420

    batcat420 Junior Member

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    Prepping to do the booster pump (47070-47060) replacement this week. I wasn't planning to replace the booster (47050-47180). Should I reconsider? I'd rather not spend another $600 if I don't have to.
     
  9. ColoradoBoo

    ColoradoBoo Senior Member

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    So no brake fluid leaks anywhere? Reservoir is good? All pads look okay? No check engine lights? Brakes are working nominal?

    If everything is good, I'd not start a "parts canon" just yet but I would do a good brake fluid drain and fill if it hasn't had one in 4-years or more.
     
  10. batcat420

    batcat420 Junior Member

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    Yes, correct. In the ~10 years we've had the car it has never had a brake fluid flush so I'll go ahead and do that and see what happens. Thanks!
     
  11. rjparker

    rjparker Tu Humilde Sirviente

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    A brake flush won't fix it for more than a day.