Loud engine sound during first start

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Retox88, Nov 8, 2025 at 12:36 AM.

  1. Retox88

    Retox88 New Member

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    Langley BC
    Vehicle:
    2007 Prius
    Model:
    Base
    Hello everyone,

    I found an 07 Prius which costs next to nothing, but it's located quite a distance from me.
    The owner described the issue as the car runs a little loud, but then quiets down.

    I have the video of it running, but I'm not allowed to post it, as my post count has to be at least 4. Will post it once it is.
    Check engine on, code unknown.

    To the people familiar with this engine, what could be the reason based on the way it runs?
    Would it make a very long drive back?

    Would appreciate any input.
    Thanks
     
    #1 Retox88, Nov 8, 2025 at 12:36 AM
  2. bisco

    bisco cookie crumbler

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    Plug-in Base
    when the engine is cold, you get a high rev start, and it gradually drops as it warms up.
    all the parts are worn on an old engine and could make more noise than newer.
    plus the oil has to circulate a bit for lubrication. but i would hesitate to make any diagnosis without hearing it, and maybe in person, and doubt it would be possible to determine if it could be driven without incident.
    other possibilities might be head gasket or semi clutch part between the engine and transmission.
    how many miles on her?
    it might be helpful to know the trouble codes, and you would need a prius aware scanner for that
     
    #2 bisco, Nov 8, 2025 at 2:12 PM
  3. pasadena_commut

    pasadena_commut Senior Member

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    Engine is really loud if the catalytic converter is missing. If the coupling between that device and the exhaust system is in bad shape it might open up at the junction when cold, and then close up when warm. So loud when cold, quiet when hot.

    There are many other things that might make the engine run rough when it is cold, but if the tone is the same, just the volume varies, inspect the exhaust system.
     
    #3 pasadena_commut, Nov 8, 2025 at 3:41 PM
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