Overheating going up inclines is it time for a new thermostat?

Discussion in 'Gen 3 Prius Main Forum' started by bootsncats24, Sep 3, 2020.

  1. bootsncats24

    bootsncats24 Junior Member

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    Hey guys before I have the thermostat changed out wanted to get some opinions. My 2011 Prius started overheating going up hills at speeds above 70. The temp reached 212 then the high temp warning will come off and once I let go of the throttle the temps drop.

    If I’m going below 70 it does not overheat. On flat ground the temps are 195 going 70. However I noticed the temps never drop unless I back off the throttle or am going down hill.

    Taken the car to a shop and they’ve replaced the water pump and the ac condenser because the fins were dirty.

    Mechanic says
    195-212 normal
    212-228 normal under load
    Above 230 may need to let it cool down

    however my high temp light came on at 212.
     
  2. Pluggo

    Pluggo Senior Member

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    You're driving in Phoenix in an exceptionally hot summer where the air is already 100-115? My money says they won't find anything wrong with your thermostat and the problem will resolve by itself in the next month.
     
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  3. bootsncats24

    bootsncats24 Junior Member

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    Live in Southern California. It gave me the high temp warning when it was 80 degrees outside at night.
     
  4. jerrymildred

    jerrymildred Senior Member

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    Your location says "Phoenix," so that's why @Pluggo assumed you were in Phoenix.

    Untitled.png

    If the A/C condenser fins were dirty, would it not be logical that the ICE radiator fins are also dirty? That was my very first thought since the air conditioner will not directly overheat the engine, although it will add load to it and increase heat a little bit. Not saying it can't be the thermostat, but why not check the easy and more likely things first? I assume you checked the coolant level, btw. Just because there's coolant in the overflow tank does not mean that the radiator is full. Hopefully they filled it properly when they replaced the pump, but it's best to be sure.

    Edit to strike out the mistake that @Mendel Leisk caught. Gen 3 doesn't seem to have a rad cap. Thanks, amigo!
     
    #4 jerrymildred, Sep 3, 2020
    Last edited: Sep 3, 2020
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  5. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Jerry are you thinking there's a cap on the radiator?
     
  6. jerrymildred

    jerrymildred Senior Member

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    Did they do away with that on Gen 3? I was thinking my PiP had one. Could be a bogus memory.

    I just checked the manual. You're right. No rad cap on the Gen 3. I was thinking it was hidden like on Gen 2.
     
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  7. fotomoto

    fotomoto Senior Member

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    First thing to do is check your coolant level. If it's low, fill with correct fluid and keep a very close eye on it. If it goes down again fairly quickly, you've got bigger problems than a thermostat.

    Check your oils' color and level.

    Check for air in the coolant system.
     
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  8. sam spade 2

    sam spade 2 Senior Member

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    Is your cooling system holding pressure ?

    It should NOT indicate "high temp" at 212 if there is pressure and a proper coolant mix.
    Where are you getting that 212 number from ??

    Could be several things......like coolant temp sensor, dirty radiator, thermostat or air "bubble" left in after the pump change. Maybe the fan(s) aren't turning properly.

    Obviously the shop was guessing with the pump.
    You need a different "mechanic" who knows how to test things.
     
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  9. ETC(SS)

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

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    ^ that, probably.

    Temperature lights are not cautionary....they're a warning that damage is presently occurring inside your engine and that it is time to immediately shut down the car and promptly investigate..
    Simply put vehicles should NEVER EVER overheat.

    Remember back when there were stories about terrorists always driving Toyota trucks (Hilluxs)?
    No, Toyota Is Not Supplying ISIS With Pickup Trucks

    Stories like these occur because Americans are dazzlingly dull witted about many things but most especially about life outside our borders.
    Terrorists do not have a military procurement system like we use.
    They drive........(wait for it!).....what everybody ELSE drives.

    So....Toyota has some small experience in making vehicles that people use where 120-degree temps might mean that it's a few degrees cooler than it was yesterday.... ;)

    Drive the car and see if the mech managed to change out the water pump correctly and bleed the system afterwards.
    Drive it as hard as you want to, up hills, when it's HOT, etc.
    It might also be a good idea to see if you're using oil and maybe if there's a little coolant contamination there as well.
    If your temp light comes on again it's possible (likely, even!) that your coolant system was not properly bled after the maintenance, but it's also possible that you have some other issues with your car.

    Yeah.
    I know.
    That's not especially brilliant troubleshooting, but either way it would warrant very prompt action.
    Your coolant should be bright and pink, like in this video.
    If it isn't....the video will help you make it that way.

    GOOD LUCK!

     
    #9 ETC(SS), Sep 3, 2020
    Last edited: Sep 3, 2020
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  10. Grit

    Grit Senior Member

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    After work, I’m changing my location to South Pole.
     
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  11. ETC(SS)

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

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    Magnetic or Geographic?
     
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  12. bootsncats24

    bootsncats24 Junior Member

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    thanks. Yeah check the coolants levels. It’s full I’m not sure how else to test to see if there’s air in the system. Heater still blows hot.

    the mechanic said he cleaned out the radiator as best as he could. The more I think about it I’m starting to think it is the radiator.
     
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  13. bootsncats24

    bootsncats24 Junior Member

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    I bought an OB2 port Bluetooth reader to read the engine temperatures on my phone. I’m looking into a different mechanic or maybe taking it to the dealership pay their fee to just diagnose it. I’ve been having an issue finding another good Prius mechanic near Ontario airport in California
     
  14. bootsncats24

    bootsncats24 Junior Member

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    first thing I checked was to see if there was water mixing with the oil. There’s not. I’m going to do that this weekend and check for air in the coolant system.
     
  15. Grit

    Grit Senior Member

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    How did you verify that?
     
  16. Xterra72

    Xterra72 Senior Member

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    Here’s my experience.....

    Had the engine coolant replaced at 170k.

    Recently, the high temperature flickered for a few seconds and then turned off. I just happened to look and noticed that. Never seen it before. Scangauge showed water temperature spike up to 255 degrees and then came back down to 195-200 degrees.

    I pulled over to a parking lot and sure enough, my engine coolant was low. Notice coolant spill by reservoir. (Thinking maybe my cap wasn’t on correctly).

    Brought it over to my mechanic the next day, light did not come on and mechanic just topped it off. He checked the oil and it was fine. ( No coolant ). He said since engine light did not come on, probably just a computer glitch where the system did not cycle the coolant through and overflowed from the reservoir tank. (Wasn’t buying it). Granted we had a heat wave that week.

    Few days went by and all good until it happened again, after about a week and a half. Got it back to my mechanic the same day and again he topped it off but this time he wired his obd2 diagnostic tool.

    So, verdict was that (as he showed it to me on the tablet), the engine electrical water pump was on its way out. Water pump was not completely out and therefore no engine light and intermittent high temperature light.

    Replaced engine electrical water pump and also replace thermostat for good measure.

    All is well now. MPG even went up. Also noticed that water temperature is cooler, averaging 193 degrees, a bit cooler than the average of 195-200 with the old water pump and thermostat.
     
    #16 Xterra72, Sep 3, 2020
    Last edited: Sep 3, 2020
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  17. bootsncats24

    bootsncats24 Junior Member

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    thanks. I’ve replaced the water pump already. I think I might change the thermostat since it won’t hurt before changing the radiator since I don’t believe it’s possible to change the radiator at home. I believe you would need to purge the AC lines to remove the condenser to get the radiator out.
     
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  18. bootsncats24

    bootsncats24 Junior Member

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    Checking the oil dipstick and looked into the radiator reservoir for oil.
     
  19. ChapmanF

    ChapmanF Senior Member

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    Right, Gen 3 was the change from the old-style "overflow" bottle to the new-style "degas" bottle. Unlike the overflow bottle, which was kind of a backwater and separate from the pressurized system, a degas bottle is part of the circulating coolant loop. When the engine is up to temp and the thermostat has opened, you can watch coolant circulating through it. (In Gen 3, the return hose is the one attaching near the top in front.) As the name implies, bubbles in the coolant loop are supposed to eventually end up in the bottle.

    Another nice thing about the new system is that the bottle isn't a backwater. If you want to use a coolant test strip, there are no worries about testing the coolant in the bottle, because it hasn't been stuck out of circulation; it's the same as the coolant in the rest of the loop.
     
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  20. ETC(SS)

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

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    Replace the radiator?
    Replace the thermostat?

    Thus far, with the symptoms described I'm a tough sell on this being a radiator problem.
    As excellently pointed out above, in the G3, you should be able to observe the coolant flowing in the bottle when the the thermostat is open. If you have positive flow then the pump and the thermostat are both working. If the bottle level isn't dropping them you are not loosing coolant - at least not much - and I'm thinking that a pressure problem would announce itself "little teapot" style.

    Thermostats are relatively inexpensive and medium easy to install.
    Thermostats can 'fail shut' if the engine in question has been overheated recently or frequently - so...yeah.
    If I woke up with the OP's car in my driveway I'd consider replacing it....
    ...MYSELF.

    ABC's of Thermostats - Stant

    I might not have thought of replacing a thermostat while replacing the water pump following temperature excursions- but then again I get paid to fix phones for a living - so it might also be a good time to start seeing other mechanics.

    Almost certainly NOT a dealership "service representative" though. ;)
     
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