Prius intermittent temp light when driving uphill

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Vinny85, Sep 1, 2025 at 2:00 AM.

  1. Vinny85

    Vinny85 New Member

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    Hi everyone i have a 2011 prius that has about 250k miles on it. I have had the car for about 10 years no major issues. I replaced the water pump, thermostat, had the headgasket changed as a preventive maintenance once i got to 240k as i want to keep the car for awhile

    I notice the the car makes noise like there is air trapped in the coolant system. I can recreate the sound when i brake hard. I have monitored the temp levels and they stay around 192-196 hwy temps and uphill if i floor it i can get the temps to 206+ as it climbs

    Is this normal or should i be worried about the air noise in the coolant and the overheating light on long uphill drives?
     
    #1 Vinny85, Sep 1, 2025 at 2:00 AM
  2. bisco

    bisco cookie crumbler

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    i'm no expert, but i would be worried. idk what temp sets the light, but it can't be a good thing
     
    #2 bisco, Sep 1, 2025 at 2:20 PM
  3. Brian1954

    Brian1954 Senior Member

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    Did you install a Toyota OEM water pump or an aftermarket pump?
     
    #3 Brian1954, Sep 1, 2025 at 3:42 PM
  4. Gokhan

    Gokhan Senior Member

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    Certainly not normal with the noise and coolant running too hot.
     
    #4 Gokhan, Sep 1, 2025 at 4:03 PM
    Brian1954 likes this.
  5. Gokhan

    Gokhan Senior Member

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    Usually, the trapped air will bleed itself. In my old 1985 Corolla LE FWD, if air was trapped during coolant drain and refill, there would be no coolant circulation whatsoever. The solution was as easy as pumping the coolant by repeatedly squeezing and releasing the upper hose and then adding more coolant. Also, the jiggle valve on the thermostat, which helps bleed the coolant, needs to face up.

    You use a 50/50 water/antifreeze mixture, right? Using a higher antifreeze concentration will result in a lower cooling efficiency and higher coolant temperatures.

    Check for leaks and a bad radiator cap. If no leaks are found, it could be an improperly installed head gasket that is sucking air or perhaps a a bad or improperly installed water pump.
     
    #5 Gokhan, Sep 1, 2025 at 7:48 PM
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