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Any videos available on replacing thermostat?

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by G Man v5, Dec 26, 2022.

  1. G Man v5

    G Man v5 Member

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    I've searched and searched and have not found any videos on replacing the thermostat in a gen 4. Anyone now of any???

    Just today, temp light showed up, and coolant level was low. Appeared to have leaked out from the overflow tank. Check engine light did NOT illuminate. No heat in car, so I'm hoping it is a stuck/closed thermostat. Hoping there is a video somewhere? It looks as if I will need to remove the air intake stuff to access the thermostat. What else is needed?

    Thanks.
     
    #1 G Man v5, Dec 26, 2022
    Last edited: Dec 26, 2022
  2. sam spade 2

    sam spade 2 Senior Member

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    Wait for a reply from someone who knows but................
    The reason that you can't find anything out about the "thermostat" might be that it may not HAVE a conventional one.

    The water pump is electric.......so the "thermostat" might be a sensor.

    Do you live where it got REALLY cold in the past few days ?
    You may have an ice block in the cooling system and maybe even a cracked block.

    Good luck.
     
  3. ChapmanF

    ChapmanF Senior Member

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    I'm guessing not much more than that, but I haven't done it on a Gen 4. The similar Gen 3 engine just has the stat built into the water inlet elbow; you replace the whole elbow.

    While the water pump is electric, the thermostat is still the conventional wax-operated kind. The pump's job is to circulate coolant through the engine, always needed when it's running; the stat's job is to notice when the coolant is so warm it needs to go through the radiator before returning to the engine. When the stat's closed, the circulation is just through the engine and the various things on the bypass circuit.

    But I'm skeptical of your reasoning from "no heat in car" to a stuck/closed stat. The heater core is part of the bypass circuit, so coolant is flowing through it even when the stat is closed. So a stuck/closed thermostat won't be an explanation of no cabin heat.

    A stuck open stat could explain slow-to-warm cabin heat, but isn't very consistent with a red overheat light.

    Where is your car from? I believe those sold in Europe or Japan have an extra electrically-operated "flow shutting valve" or "selector valve" on the back of the head, but North American ones do not.

    [​IMG]
     
  4. G Man v5

    G Man v5 Member

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    Oh it's a US car... But I thought all the Priuses were made in Japan?

    Thanks for the info. This is very concerning.
     
  5. ChapmanF

    ChapmanF Senior Member

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    They're made in japan, but the ones made for sale into different world markets can be different builds. The "flow shutting valve" in the models for Europe and Japan is a case in point.

    That's also why Gen 3 drivers in countries that drive on the left can change their spark plugs without taking the wipers off, and we can't.
     
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  6. Mendel Leisk

    Mendel Leisk Senior Member

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    Yeah would be helpful if OP disclosed (roughly) where he lives.

    Also: the miles on the car? If high enough, maybe pump failing?

    So the car is overheating, and engine coolant pressure might be high. Without engine light coming on, no codes?

    Could this possibly be related to 4th gen exhaust heat recovery issue? The coolant loss is one related symptom.

    Might take a dealership diagnostic visit?

    Attached is 4th gen Repair Manual engine cooling system excerpt.
     

    Attached Files:

  7. G Man v5

    G Man v5 Member

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    Year is 2016. 101K miles. And yes, located in Midwest and it was rather cold last week....

    Could the water pump be failing at this low of mileage? And does it "throw a code(s)"?

    Thanks for the link....
     
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  8. Mendel Leisk

    Mendel Leisk Senior Member

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    Midwest eh... Ok, ok, I know... And this is a US'centric forum.
     
  9. BiomedO1

    BiomedO1 Senior Member

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    I wouldn't jump to conclusions. Refill and burp the system. Keep an eye on coolant levels over the next few days. It's more likely a leak into the exhaust gas heat exchanger. Low coolant also means no cabin heat and heat pumps don't work very well in the cold snap you just had. Besides; your due for coolant change anyways.
    If you continue to loose coolant; loop out the exhaust gas heat exchanger to see if that stops the leak.

    Good Luck.
     
    #9 BiomedO1, Dec 27, 2022
    Last edited: Dec 27, 2022
  10. Doug McC

    Doug McC Active Member

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    How close to the Chicago Land South Side? Close enough for a trip to have the Car Care Nut look at it?
     
  11. G Man v5

    G Man v5 Member

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    I wish I was up there. I'm in St. Louis..
     
  12. G Man v5

    G Man v5 Member

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    Are the reason I thinking it's not the exchanger which I've been reading about and I see it can be bypassed, is it? There was signs of coolant leaking near the tank. Tank. There was coolant on top of the tank and some areas just around the tank like it had overheated and sprayed out of the pressure relief valve or cap. I'll check under the car and is there a link or does anybody have a video on how to bypass that heat exchanger on the bottom? I've seen a couple still photos but still not positive on what to do.
     
  13. BiomedO1

    BiomedO1 Senior Member

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    That's because your car did overheat; you mentioned it in your original post ("temp light showed up").
     
  14. G Man v5

    G Man v5 Member

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    I never said it didn't. I'm not sure the point of your post.
     
  15. Jama707

    Jama707 Junior Member

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    did you figure out the issue?
    I've the same issue with 2016 - I did the bypass as explained by headgaster masters video. But still losing coolant and spilled all around the reservoir. And I got the P261B code
     
  16. ChapmanF

    ChapmanF Senior Member

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    That code makes your situation distinct; you should make sure to get the water pump working.
     
  17. G Man v5

    G Man v5 Member

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    Yes, it was a bad waterpump. It failed around 100K miles. That sucked. That is why when it overheated the coolant sprayed out from the pressure relief valve. Had the pump and the thermo replaced.