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Engine Coolant Overheat

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by PriusVMonster, Jun 7, 2021.

  1. PriusVMonster

    PriusVMonster New Member

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    Hi Team,

    Bought a used 2014 Prius V, unfortunately had a lot of issue. Fixed some issues but now has engine coolant overheat when running in high RPM(either >75mph or upslope), observe turbulence in coolant tank. Coolant spit out from a hole under coolant tank cap. Another observation that may not relevant - heater is warm only when set to max temp.

    Did below and need help:
    1. Changed water pump
    2. Changed thermostat
    3. Changed radiator
    4. Changed head gasket (Had coolant loss, white smoke from exhaust, misfire, vibration in low speed or idle so it was a problematic head gasket. All these issues are gone now.)
    5. Checked engine coolant sensor, the resistance change at different temp
    6. Radiator and condensor fan rotates when coolant temperature is high, but it is on and off. When AC is on, both fans are on and off too instead of consistently on. Is it normal?
    7. Tried to check hose to confirm if radiator works correctly. Any idea which hose should be hot or warm? Both hoses on top and bottom of engine coolant tank are hot when over temp. Other hoses are hot too.

    Any advice is appreciated, thank you.
     
  2. Mendel Leisk

    Mendel Leisk Senior Member

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    How many miles? Any evidence of stop-leak product in coolant? Had Exhaust Gas Recirculation system, including intake manifold, been cleaned?
     
  3. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    Everything is hot during an overtemp condition! :p
    I hate to ask such a basic question after all of that work but did you bleed the coolant system after the HG change?

    Our own @NutzAboutBolts has a vid covering this (and LOTS of other stuff!)




    Give them a quick 'like' and a maybe even a 'sub' if you find their info helpful!
    Content providers like these save folks a ton of money!! ;)
     
    #3 ETC(SS), Jun 7, 2021
    Last edited: Jun 7, 2021
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  4. Georgina Rudkus

    Georgina Rudkus Senior Member

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    Another good video.

     
  5. rjparker

    rjparker Tu Humilde Sirviente

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    No this is not normal. Check the circuit or just change the assembly. Do not used most aftermarket fans. Go OEM or the UAC brand I used when I proactively changed mine last year. Still have a working OEM in the garage.



    I find the 2012 and newer self bleed easily. With a new radiator I would not worry too much about a pre-head gasket sealer. It is always useful to have data, eg what does the temp do when. I use "Car Scanner" app with an Obd2 bluetooth.
     

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    #5 rjparker, Jun 7, 2021
    Last edited: Jun 7, 2021
  6. PriusVMonster

    PriusVMonster New Member

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    Mendel: It is 128k miles. EGR, intake manifold were cleaned during head gasket replacement. Yes, there was sign of stop leak. Some small stones were seen in the thermostat after replacement. Flushed the coolant 2 times but I am not 100% sure all stop leak were flushed. Any suggestion? I am thinking about pressure flush but don't have tool to do it.
    ETC: Video from @NutzAboutBolts is helpful. I didn't do bleeding this way, so I did it tonight. Will see what happen on next drive. Previously I open engine coolant cap and remove EGR sensor, pressed hoses to bleed it.
    Georgina: Thanks, watched this video too!
    rjparker: The fan is as is from previous owner, thanks for it and the recommendation of bluetooth obd2 too. I think it is interesting to have live engine coolant temperature data.
     
  7. ASRDogman

    ASRDogman Senior Member

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    If it had any head gasket sealer, did you flush it with vinegar? That is supposed to break the sealer down.
    There are passages in the head and block that could be blocked along with the heater core.
    Just because the sensor changed temp doesn't mean it's working correctly.
    I believe there are smaller coolant hoses also, that go to the EGR cooler, those could be blocked.

    Head gasket sealer is horrible! It clogs up everything, except the head gasket.
    You might have to remove the themostat and fill with white vinegar, maybe 50/50 mix or 75/25 with more
    vinegar, and run the coolant pump without the engine running, by jumping it, for 10-25 minutes then flush
    with straight water. Hopefully that will get all the sealer cleared out. Maybe do it twice?

    Have you washed out the coolant tank?
     
    #7 ASRDogman, Jun 8, 2021
    Last edited: Jun 8, 2021
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  8. Mendel Leisk

    Mendel Leisk Senior Member

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    Yeah as @ASRDogman said, vinegar may dissolve the “stones”. A PriusChat member contacted one stop leak manufacturer, and they suggested a 50/50 vinegar/water flush, which dissolves the product. To see if it works: if you can get a few of the stones, drop them into such a mixture and see what happens.

    one issue: if it works and you go through with it, say do a 50/50 flush followed by straight water flushes, now you have a system with nothing but water. No drain will be 100%, maybe 80%. You end up with residual water in system, messes up the ratio.

    nother issue: IIRC there isn’t a published engine coolant system capacity spec. At least I haven’t found it.

    Yet another issue: the Toyota Super Long Life Coolant specd only comes in 50/50 pre-mix (55/45 in Canada).


    With my fuzzy recall from the coolant change I did, I’d hazard it’s just under 2 gallons. Accordingly, one way to get the system back to normal, after all the water flushes:

    First pour in a gallon of Toyota Long Life Coolant *, then continue filling with distilled water. This will hopefully get you close to 50/50 coolant ratio. You could check after, say with hygrometer, and if over-strength, drain and replace a little with more distilled water.

    * Toyota Long Life Coolant (note no “Super” in name) is 100% Coolant, sim formulation to the SLLC but Toyota recommends a shorter change interval for it, and it’s not specd for Prius. Accordingly, run this mix for maybe 2 years, then do another drain and fill, with the reg SLLC.

    Maybe @Elektroingenieur can comment, on the availability and viability of Toyota Long Life Coolant, the full strength coolant? And engine coolant capacity?
     
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  9. rjparker

    rjparker Tu Humilde Sirviente

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    Don't forget the fan is not running right. Previous owner or not. Without data you are guessing. Which is fine for those of us with no overheating, not so good for you since its deadly to your engine.