2012 Prius spark plug change

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by CanyonWells, Jun 16, 2026 at 10:34 PM.

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  1. CanyonWells

    CanyonWells New Member

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    I have a 2012 Prius at 120k. I bought it off an older couple who took very good care of it.

    I changed the spark plugs today and noticed some heavy residue on the spark plug threads. Could this possibly be a valve cover gasket leak or a tube valve seal leak?
     

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    #1 CanyonWells, Jun 16, 2026 at 10:34 PM
  2. PriusCamper

    PriusCamper Senior Member

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    They look fine too me...
     
    #2 PriusCamper, Jun 17, 2026 at 4:10 AM
  3. 20113rdgen

    20113rdgen New Member

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    Would be more concerned about carbon buildup in the cylinders. Look at the egr system and channels. The egr system is really the weakest link on the 3rd gen.
     
    #3 20113rdgen, Jun 17, 2026 at 4:52 AM
  4. CanyonWells

    CanyonWells New Member

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    I’m wondering what all the orange crust is on the plugs and tops of the pistons?
     

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    #4 CanyonWells, Jun 17, 2026 at 7:00 AM
  5. Tombukt2

    Tombukt2 Senior Member

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    Pretty normal looking business there .
     
    #5 Tombukt2, Jun 17, 2026 at 8:41 AM
  6. Mendel Leisk

    Mendel Leisk MMX GEN III

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    #6 Mendel Leisk, Jun 17, 2026 at 9:21 AM
  7. ColoradoBoo

    ColoradoBoo Senior Member

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    I agree with the EGR cleaning....I'd, also, start using Valvoline Restore and Protect Synthetic motor oil in that engine...it's great in older engines.
     
    #7 ColoradoBoo, Jun 17, 2026 at 10:20 AM
  8. CR94

    CR94 Senior Member

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    Wouldn't any residues from oil leaks on the outside (i.e., top) side of the spark plug gaskets be found only on the outside of the gasket?

    Were the plugs unexpectedly difficult to turn?

    I've been procrastinating changing my original plugs, but have bought replacements and the tool.
     
    #8 CR94, Jun 17, 2026 at 11:58 AM
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