please read my future from these tea leaves (er, sparks plugs)... is it that time?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by viciousthinker, Jun 10, 2026 at 10:37 PM.

  1. viciousthinker

    viciousthinker Junior Member

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    Hi again all... ok, so I somehow got it into my head to pull my plugs this evening and see how they are fairing... my 2012 has around 280k on it now, and I live in a constant state of (fearing? longing for??) the final conclusion to Shroedingers head gasket. I've attached pics that show the pulled plugs lined up and numbered left to right... if any of the learned here could take a look I would appreciate it... I just don't know what I'm looking at. Numbers 1, 2, and 4 look like they gave somehow *RUSTED* down in the combustion chamber, that doesn't seem right to me...

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    If it's time, I guess I'm ready. I have a new FelPro headgasket here on hand, torque wrench, timing kit w/ new guides, chains, and sprockets, engineers straightedge, feeler gauges, that weird ratchet attachment that helps to measure 90°, 180°, 270° rotations, etc... still a little unnerved by the timing chain procedure but if it's ready...

    Ps, I am cognizant of the fact that the outlier plug that isn't rusted is a proper DENSO, whereas the rusted ones are some third-party brand... but still, actual rust?

    Or not? I honestly don't know how to read these plugs

    thx in advance all..
     
    #1 viciousthinker, Jun 10, 2026 at 10:37 PM
  2. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    You're using a rectal thermometer to diagnose a sore throat.....

    Let's talk about why you pulled the plugs.
    Any other symptoms?

    You don't need a cat and a box to determine whether or not your head gasket has failed or not (or both....)
    Do a leak-down test......
    Check your coolant level regularly.....
    You live in TX, right?
    That means that there is a high likelihood that HAVE a borescope, or you know somebody with a borescope - and you've already done the hardest part......
     
    #2 ETC(SS), Jun 11, 2026 at 10:29 AM
  3. Mendel Leisk

    Mendel Leisk MMX GEN III

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    When were they last changed; do you know? Toyota says every 12 years or 120k miles, whichever comes first.

    With your miles, their appearance, since you've already removed them, and doubly so if you don't know the car's full history, I'd just replace.them.

    Any cold-start shaking, coolant loss?
     
    #3 Mendel Leisk, Jun 11, 2026 at 11:57 AM
  4. Brian1954

    Brian1954 Senior Member

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    #4 Brian1954, Jun 11, 2026 at 12:51 PM
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