Replacing spark plugs

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by avoice217, Dec 19, 2025.

  1. indel

    indel Member

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    Where exactly is this vent on a 2012?
     
  2. Mendel Leisk

    Mendel Leisk MMX GEN III

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    It was here:

    wider view:

    upload_2026-1-14_9-33-31.png

    Close up:

    upload_2026-1-14_9-37-2.png

    In later model years, the main component is still there, and the same hoses connect, but the white cap is gone, which you could turn to allow air or coolant to flow through the spigot on the side.
     
    #62 Mendel Leisk, Jan 14, 2026 at 12:27 PM
    Last edited: Jan 14, 2026 at 12:37 PM
  3. indel

    indel Member

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  4. ChapmanF

    ChapmanF Senior Member

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    Yes, if your car has that valve and you want to use it, you can, and it will behave as described.

    Toyota later decided there was no need for it, or any of that related business in the instructions, and the later gen 3s still can be filled with coolant.
     
  5. rjparker

    rjparker Tu Humilde Sirviente

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    I have never done anything on my 12v's coolant drain and fills other than leaving the reservoir cap loose during the initial warmup.

    Trapped air is not a problem unless combustion gasses are entering the pressurized system.
     
  6. CR94

    CR94 Senior Member

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    Yes.
    It was already "gone" by the time they made my [late-year] 2011, so would likely be missing from a 2012.
     
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  7. ChapmanF

    ChapmanF Senior Member

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    You can also leave a gen 3's reservoir cap closed during the initial warmup, like the repair manual says to. There is enough headspace in the degas bottle to receive the air that circulates back.

    I'm not sure why they went out of their way to say put the cap on, but one guess could be that when you let the system reach pressure, any bubbles are half as big, and maybe circulate back to the bottle more easily.
     
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  8. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Last fall I did engine coolant replacement (and inverter coolant), folllowed the repair manual instruction to fill reservoir to “B” line, cap reinstalled, run in maintenance mode. Worked well, coolant dropped, to slightly above full line IIRC.

    One thing, after running engine for about 20 minutes I figured it was done. Topside hoses felt hot. I had the front raised and engine under panel removed, so shut off the car and went under to replace under panel, felt a couple of hoses under there, and unlike the (toasty) topside ones, they were still stone-cold.

    accordingly, I restarted car in maintenance mode, crawled back under, and just lay there, reflecting on life an such, occasionally checking on the hose temps. Eventually they started warming, presumably due to thermostat opening, and got hot quite quick, in just a few minutes.

    Then I dubbed it done.