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Overheating issue on 2010 Prius

Discussion in 'Prius v Technical Discussion' started by Gman38474, Dec 28, 2021.

  1. Gman38474

    Gman38474 New Member

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    Location:
    Tennessee
    Vehicle:
    2010 Prius
    Model:
    Five
    I have been dealing with an overheating issue on my son's 2010 Prius. So far the radiator, thermostat, water pump, and coolant reservoir have all been replaced. After about ten to 15 minutes of driving, I notice that the coolant temp starts to climb slowly, but this will also depend on the terrain. But when it starts to do this, I notice that the heat inside the car starts to cool down and then gets cold. I also noticed that there is about a 10-15 degrees temp difference between the driver and passenger side vents at the start of driving. Checking the hose coming from the radiator to the thermostat, this hose will not be hot at all. Also, the reservoir seems to fill with coolant and force some out due to pressure. So seems like its not circulating the coolant. Because of this, I opted to replace the water pump again. Although this time I actually removed the thermostat from the housing. I put the car in maintenance mode and ran it this way just to see that the coolant was circulating. This seemed to work fine. But one thing I notice here is that there are bubbles coming into the reservior even after there the system was bleed. Would this be a sign of a blown head gasket? I don't see coolant in oil and I don't notice it smoking. Thank in advance for any help.
     
    #1 Gman38474, Dec 28, 2021
  2. ChapmanF

    ChapmanF Senior Member

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    I seem to recall there are tests that can identify exhaust gases in the coolant loop. That would probably give you a solid answer to the question.
     
    #2 ChapmanF, Dec 29, 2021
  3. Gman38474

    Gman38474 New Member

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    Five
    Thanks, I’m going to pick up a combustion test kit from Harbor Freight this afternoon.
     
    #3 Gman38474, Dec 29, 2021
  4. gromittoo

    gromittoo Active Member

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    Two
    IIRC, the 2010 does not have the self bleeder in the hose going to the heater core. Trapped air would cause that hose to be cool. My 2013 Prius v has the bleeder, and it seems to work.
     
    #4 gromittoo, Dec 29, 2021
  5. ChapmanF

    ChapmanF Senior Member

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    You mean this guy?

    [​IMG]

    It's kind of the opposite: in the Gen 3 liftbacks, 2010 and 2011 had it, no more in 2012 and later.

    The hose it is in, for what it's worth, is the hose returning from the exhaust heat exchanger under the car. It returns to a collecting nipple on the top of the EGR cooler and from there returns to the engine through the thermostat bypass. All of that is well downstream of the heater core.

    Toyota never said much about why they discontinued that valve with the 2012s, but I suspect they just decided they didn't need it. All the Gen 3s do have the degas-bottle style cooling system, where small nipples pick off the air from the high spots of the radiator and the cylinder head outlet and deliver it to the top of the bottle. That little upside-down U of hose coming back from the EHRS, without the extra valve, will certainly hold a bubble while being filled, but there's no law saying a bubble can't be carried with flow, and they may have seen in the first two years that it just ends up in the bottle eventually anyway, and doesn't take long enough to justify any extra fuss.
     
    #5 ChapmanF, Dec 29, 2021
  6. gromittoo

    gromittoo Active Member

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    I believe my 2013 Prius v has one of those valves, or something very similar. I don't remember the wires connecting to it though.
     
    #6 gromittoo, Dec 31, 2021
  7. ChapmanF

    ChapmanF Senior Member

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    Well, it looks like the same part number listed, 87251-47020, over the whole range of years, and yet people have reported seeing it with the spigot and without. I guess that would make it just two variations on the same part then.

    87251-47020 Genuine Toyota Joint, Water
     
    #7 ChapmanF, Dec 31, 2021
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