Is coolant reservoir under high pressure when hot?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by ePRIU$, Apr 5, 2021.

  1. ePRIU$

    ePRIU$ Junior Member

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    There's no radiator cap in 2012 Prius 3, any coolants work go directly from the reservoir. My question is can I open the cap when coolant is hot? will it has high pressure like regular radiator with a cap? thanks.
     
  2. ChapmanF

    ChapmanF Senior Member

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    Yes, it is under pressure. Unlike older cars with a "coolant recovery bottle" that attached at the radiator cap filler neck, Prius starting with Gen 3 has a "degas bottle" that is part of the circulating coolant system, so it is under pressure. Let it cool before opening the cap.
     
  3. sam spade 2

    sam spade 2 Senior Member

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    And it very likely says that, right ON the cap itself. :)
     
  4. rjparker

    rjparker Senior Member

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    While I don't recommend it, I have slowly released the cap under pressure without steam or water erupting. The system does work nicely and always eliminates the air quickly after a coolant change.
     
  5. sLick415

    sLick415 Member

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    There's actually a bleeder nipple behind the cap to release the pressure and allow you to open the cap while the coolant is hot.

    Posted via the PriusChat mobile app.
     
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