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Proper way of draining and filling coolant.

Discussion in 'Gen 3 Prius Technical Discussion' started by Rudd, Jun 28, 2022.

  1. Rudd

    Rudd Junior Member

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    Hello, So i been filling up my engine coolant by itself since i replaced my water pump. I put it in maintenance mode and was almost sure all air bubbles were out. I'm still getting air bubbles and they shoot back to the coolant violently when it's hot. I just saw guy do both engine and inverter drain simultaneously so i'm kind of wondering if i was supposed to do that to make sure no air in the cooling system. Can you do one at a time or i have to do both at the same time?
     
    #1 Rudd, Jun 28, 2022
  2. JC91006

    JC91006 Senior Member

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    if the bubbles are coming back "violently", then you most likely have a bad headgasket. You should check for that
     
    #2 JC91006, Jun 28, 2022
  3. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    #3 Mendel Leisk, Jun 28, 2022
  4. ChapmanF

    ChapmanF Senior Member

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    There are test kits involving a liquid that changes color when exposed to exhaust. You can put one over your coolant bottle in place of the cap, run the engine and see some of those bubbles "violently" shooting back, then slurp up the air from the bottle and see if the liquid changes color.

    If it does, the bubbles are really exhaust, and you've got a likely head gasket leak.

    If it doesn't, they're just air straggling out. This cooling system is designed to eventually burp those back to the coolant bottle like that, so as long as the bubbles aren't exhaust, it may not be a big deal. Just be sure to top the level back up to F (when cold) if it drops below that. If it repeatedly drops, look for a leak.
     
    #4 ChapmanF, Jun 28, 2022
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