Normal Coolant Temps for Gen 3 Prius on Long Uphill Climbs?

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by marksky57, Aug 14, 2026 at 1:29 AM.

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  1. marksky57

    marksky57 Junior Member

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    2010 Prius, 260k miles. Coolant temp reaches about 209°F on flat highway driving in Arizona summer heat. Recently repaired a P261C electric water pump circuit issue. No current warning lights or codes. Concerned that sustained mountain climbs in 100°F+ weather could push coolant temps beyond 215°F. What temperatures are other Gen 3 owners seeing on long grades, and what components should I check first: water pump, radiator efficiency, thermostat, airflow, or cooling system contamination?
     
    #1 marksky57, Aug 14, 2026 at 1:29 AM
  2. Brian1954

    Brian1954 Senior Member

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    I see 195 to 199F on flat road 70mph. Going up a long incline, I see 202 to 207F.

    The engine water pump and checking the air flow through the radiator would be the two things I would check.
     
    #2 Brian1954, Aug 14, 2026 at 8:21 AM
  3. Dave1UK

    Dave1UK Junior Member

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    On flat highway driving at 70mph I see max of about 93°C (200°F) but I'm based in the UK with weather of about 25°C (77°F). Not sure about mountain climbs, but a steepish hill I have seen it reach about 98°C (208°F) before.
     
    #3 Dave1UK, Aug 17, 2026 at 5:30 AM
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