Don't pre-judge this post- not a head gasket issue

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by C Clay, Oct 14, 2024.

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  1. C Clay

    C Clay Member

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    Couldn’t a faulty thermostat cause coolant to be pushed out of the reservoir?
    If the thermostat was stuck in the closed position, coolant wouldn’t circulate properly through the engine. As the engine heated up, the coolant would expand , increasing pressure within the system. This excess pressure could force coolant out of the reservoir, especially if the reservoir cap wasn’t properly venting.
     
    #21 C Clay, Dec 29, 2024
  2. C Clay

    C Clay Member

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    Also, just an observation - the light doesn’t seem to come on, but if I take the reservoir cap off (like to add coolant) and let the engine run for a good bit- my scanner app will report that code, then when I clear it never comes back.
     
    #22 C Clay, Dec 29, 2024
  3. johnHRP

    johnHRP Active Member

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    Engine coolant temperature is red by coolant temp sensor. It went to complete cold/zero when the pipe from the thermostat to radiator burst on my 2004 Sienna. The whole coolant are out and the sensor read nothing/zero. What I worry more about yours is: Where do the coolant go? It must go somewhere and escape. Check if the exhaust is hotter than other Prius at the same running condition.
    When I had head gasket leak on my 02 Altima, the exhaust was really hot and sweet smell. Not enough to notice white smoke and the coolant droped very slowly. Probably down from max to min every other week.
     
    #23 johnHRP, Dec 29, 2024
  4. C Clay

    C Clay Member

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    The coolant when out the small port in the overflow tank
     
    #24 C Clay, Jan 1, 2025
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