2010 Prius Engine Running more loudly than before

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Web Storm, Jul 18, 2025 at 1:25 PM.

  1. Web Storm

    Web Storm Junior Member

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    The engine on my 2010 Prius (108k miles) is running more loudly than it was before. It's been this way for the last seven months. Started in the winter but it's still happening in the summer.

    It's not knocking, and it's consistently louder than usual whenever the engine is on (i.e. I don't need to be in the red zone of the power bar). There are no OBD2 codes.

    I have searched on the forums here and online but haven't found many posts about just the engine running more loudly.

    I don't think this is related but the loudness started happening within a week after I had my inverter coolant flushed by a dealership. I distinctly remember when it started – I was just pulling into a parking lot to park and noticed the engine was louder than normal, and it's been that way ever since.

    About a month before I had the inverter coolant changed I cleaned out the intake manifold and replaced the gasket, and cleaned the EGR pipe (just the pipe, not the full circuit).

    About a month after I had my inverter coolant changed I also changed the spark plugs to the SC16HR11 ones and did a regularly scheduled oil change but that hasn't helped.

    There don't seem to be any other actual noticeable issues as a result of the loud engine but obviously I want to make sure the engine is not running too hot and cause the blown head gasket. I'm not losing any coolant and the coolant levels are normal.

    Anyone have ideas on what it could be?
     
    #1 Web Storm, Jul 18, 2025 at 1:25 PM
    Last edited: Jul 18, 2025 at 1:33 PM
  2. bisco

    bisco cookie crumbler

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    exhaust leak?
     
    #2 bisco, Jul 18, 2025 at 1:27 PM
    Brian1954 likes this.
  3. Web Storm

    Web Storm Junior Member

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    Hmm, with an exhaust leak should I also expect to smell fumes either inside or outside the car?
     
    #3 Web Storm, Jul 18, 2025 at 1:34 PM
  4. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Better get on that ASAP.
     
    #4 Mendel Leisk, Jul 18, 2025 at 1:52 PM
  5. PriusCamper

    PriusCamper Senior Member

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    We'll need you to be way more detailed about what you mean regarding engine running loud. It's currently way to vague... where are you in relation to vehicle when it is loudest? Have you examined the entire exhaust system to ensure its not a leak? Basically, people's ears play tricks on them and the constantly drive auto mechanics crazy with claims of strange noises they can't describe very well.
     
    #5 PriusCamper, Jul 18, 2025 at 1:59 PM
  6. GoodOldBob

    GoodOldBob Junior Member

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    I would have a muffler shop check out the whole exhaust system. Mufflers can internally corrode and lose their muffling capability without an actual exhaust leak happening.
     
    #6 GoodOldBob, Jul 18, 2025 at 1:59 PM
  7. rjparker

    rjparker Tu Humilde Sirviente

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    ... double post
     
    #7 rjparker, Jul 18, 2025 at 2:13 PM
  8. rjparker

    rjparker Tu Humilde Sirviente

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    If it is really louder now the egr pipe could be missing a gasket or the gasket is not in correct. That would be loud as it is an exhaust leak.
     
    #8 rjparker, Jul 18, 2025 at 2:13 PM
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