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coolant circulation?

Discussion in 'Gen 2 Prius Main Forum' started by PA Prius, Jul 21, 2012.

  1. PA Prius

    PA Prius Active Member

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    My daughter was driving our '04 up a 3 mile 10% incline, fully loaded and outside temp was in the 90's. Coolant temperature got to around 205°, she was a bit concerned so she turned off the AC, opened the windows and turned the heat on high. She asked me later if she should have left the ICE running going down the other side or kept it below 42 mph with the ICE off-- which would cool the ICE faster? So my question-- does the coolant still circulate when the ICE is off and car is moving? (I also informed her that the coolant boiling point is higher than that of water, so she was fine at that temp.)

    PA P
     
    #1 PA Prius, Jul 21, 2012
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The engine coolant will not circulate if the gasoline engine is not spinning. The engine coolant pump is mechanical, spun via the serpentine belt powered by the crankshaft pulley. If the engine crankshaft is not spinning, then the coolant pump will not be either.

    Congratulations to your daughter for noticing that the engine temp was getting high and taking reasonable measures to deal with that.
     
    #2 Patrick Wong, Jul 21, 2012
  3. PA Prius

    PA Prius Active Member

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    Thanks!

     
    #3 PA Prius, Jul 21, 2012
  4. wjtracy

    wjtracy Senior Member

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    How do you know coolant temp is that SCANGAUGE??
    Be sure to check coolant level.
     
    #4 wjtracy, Jul 21, 2012
  5. PA Prius

    PA Prius Active Member

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    Yes, Scangauge. Thanks for the coolant check reminder. It is just below the "L" mark. This is the one right above the coolant fan in front, right? The other one further back toward the middle is for the inverter coolant, right?

    PA P
     
    #5 PA Prius, Jul 21, 2012
  6. wjtracy

    wjtracy Senior Member

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    ...well I have a leaky water pump at 106k so I refill level when needed.
    Mine has now stopped leaking, so I am trying to see how long I can stretch it.
    I am confused if there could possibly be air hold up in the coolant system that I am not aware of.
    But I am looking good right now, no leaks.
     
    #6 wjtracy, Jul 21, 2012
  7. HaroldW

    HaroldW Active Member

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    205 is not that terribly hot in hot temps! I hit 205 on most hills during hot weather. I have never been over that yet. If I see 220 then I look for a shady spot.H
     
    #7 HaroldW, Jul 21, 2012
  8. uart

    uart Senior Member

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    I agree with Harold, 205 is not super hot.

    The 50/50 ethylene glycol mix doesn't boil until 223F at atmospheric pressure, and the pressurized cooling system further raises that to about 265F (at max rated pressure, though you really don't want to go there.).

    I would have just let the engine cut out after cresting the hill, this will allow the coolant in the radiator to cool reasonably quickly and halt further heat input to the system. Then as soon as the downhill speed hits 43+ MPH the engine will start spinning anyway and the coolant temperature will rapidly get back to a nice safe level.
     
    #8 uart, Jul 22, 2012
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