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Prius C coolant thermostat

Discussion in 'Prius c Care, Maintenance and Troubleshooting' started by luis perez, Jul 9, 2023.

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  1. luis perez

    luis perez Junior Member

    Joined:
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    Location:
    Texas
    Vehicle:
    2009 Prius
    Model:
    Base
    Hello everyone!

    I am wondering if the coolant thermostat in the 14 Prius C one is leaking.What follows is a description off what I could see as I checked temps this morning, a P10 ODBII monitor was used to read the temp the ECU sees. It read 17C although ambient temp was around 28C (I guess the sensor is not accurate at that temp range). Started the engine and kept the engine running.
    At around 60C the hose that exits from the engine head started to feel warm (#2 according to repair manual).
    At 70C I could no longer touch the #2 hose.
    At 80C the hose that goes to thermostat started to get warm.
    At 83C I could no longer touch the hose that goes to the thermostat, the temp “parked” at 83C for a while. 84C displayed sporadically
    Once the P10 displayed 85C, the temp started to climb rather quickly.
    At 89 or 90 the radiator cap started to release water: The thin hose that goes to the coolant reservoir got very hot, the change in temp was quick. I wonder at what PSI value the cap started to yield.
    At 95C the fan started at a very slow speed and the temp displayed in the P10 quickly went down. Fan stopped at 90~91C. Wash, rinse, repeat once temp reached 95C.
    Any comments?
     
    #1 luis perez, Jul 9, 2023
  2. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    May 12, 2018
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    Vehicle:
    2018 Prius c
    Model:
    Two
    It might be too early in the morning, but I think I'm reading about completely normal operation here.

    Except maybe the slowness of the fan.

    Is there a problem or symptom with this car?
     
    #2 Leadfoot J. McCoalroller, Jul 9, 2023
  3. luis perez

    luis perez Junior Member

    Joined:
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    Location:
    Texas
    Vehicle:
    2009 Prius
    Model:
    Base
    [QUOTE="Is there a problem or symptom with this car?[/QUOTE]

    Hello!

    In the past, the radiator fan failed at about 40K miles, carbon brushes where completely worn out when I took the motor apart. Before that the engine trembled, after the fan failure I started to pay more attention to that tremble, eventually winded up disconnecting the EGR motor. Coolant & engine oil levels are stable. After disconnecting the EGR the MPG did go up. The engine sounds and runs fine. Acceleration is also "lighter". As of now, the exhaust tail pipe looks quite clean.

    Yes, the thermostat function looks OK. just tat part of the hose being warm before 70C makes me wonder. And yes: If it is working, do not fix it lol.

    Any comments or if more info is needed please let me know. As of now, the car feels fine ... fingers crossed.

    Luis
    PS Toyota does not recommend disconnecting the EGR to fix problems.
     
    #3 luis perez, Jul 9, 2023
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