Start Up Knock "death rattle" after egr clean, pcv replace, coolant flush etc.

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by confusedcole..., Jan 8, 2026.

  1. confusedcole...

    confusedcole... Junior Member

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    ----USA----
    Hi I have recently bought this gen 3 prius with almost 200k miles on it. I replaced coolant pcv, cleaned the egr and intake manifold but after driving it for about 3000 miles it suddenly starting giving morning death rattle noises just a few seconds after starting while its in park. combustion leak detector just came back as a negative for a bad head gasket? But maybe it still is. I plan on releasing pressure from coolant after driving it to see if that makes start ups any better. Thanks any thoughts would be helpful.
     
    #1 confusedcole..., Jan 8, 2026
  2. Cornvalue

    Cornvalue New Member

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    The rattle can be caused by many reasons. It’s a design flaw in the engine.

    Check coolant levels and oil consumption after mileage covered above 1000km. Unless there is a loss or exhaust indicate any kind of excess burning it might not be a major issue.

    Try to never run this engine for short periods only; that will cause a rattle due to moisture in the manifold. Always let it warm fully (get warm air blown from vents), even if you - like me - have to move it 500 meters due to parking restrictions in my city….
     
    #2 Cornvalue, Jan 13, 2026
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