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Prius overheating on highway. Changed thermostat. Water pump is operational.

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by CAITLIN FOLEY, Apr 28, 2020.

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  1. CAITLIN FOLEY

    CAITLIN FOLEY New Member

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    I have heat in the cabin. I can feel the hot water coming out of the smaller thermostat outlet. But only cold coolant in larger hose to radiator. I theorized the radiator was clogged and almost replaced it. Then had idea to disconnect it and force hose water through it. I dont know if I cleared it or it was already clear but water flows fine through it. However, now when I drive it, still no coolant goes to the radiator. It looks like it just goes back into the engine past the little brass overflow pipe that goes back to resorvoir. I just can't figure out why it goes through engine and out into the cabin heater but it wont go through radiator circuit. I'm constantly scared I'm gonna overheat it and do some real damage. And its getting hotter by the day, so running the cabin heat on high is not feasible. It's not thermostat, water pump, or radiator. Any ideas?
    Thanks
     
    #1 CAITLIN FOLEY, Apr 28, 2020
  2. Air_Boss

    Air_Boss Senior Member

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    In a traditional ICE vehicle, this is a symptom of the Thermostat stuck closed.
     
    #2 Air_Boss, Apr 29, 2020
  3. sam spade 2

    sam spade 2 Senior Member

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    How do you KNOW that the impeller on the water pump is not broken and thus not actually moving any or enough water ?
    I think that is a fairly common failure.
     
    #3 sam spade 2, Apr 29, 2020
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  4. Air_Boss

    Air_Boss Senior Member

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    Really? As in shaft sheared? Blades shed? How? Insufficient antifreeze?
     
    #4 Air_Boss, Apr 29, 2020
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  5. Georgina Rudkus

    Georgina Rudkus Senior Member

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    Blades are plastic. Year, ago, they would have been an aluminum allow, Plastic is cheaper to make.
     
    #5 Georgina Rudkus, Apr 29, 2020
  6. Air_Boss

    Air_Boss Senior Member

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    OK, but what fails? Blades? Blade to shaft attachment? Shaft?
     
    #6 Air_Boss, Apr 29, 2020
  7. sam spade 2

    sam spade 2 Senior Member

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    Don't know how or why, it just DOES.
     
    #7 sam spade 2, Apr 29, 2020
  8. Air_Boss

    Air_Boss Senior Member

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    If it happened frequently, wouldn't it show up as a TSB or at least a goodwill replacement?
     
    #8 Air_Boss, Apr 29, 2020
  9. sam spade 2

    sam spade 2 Senior Member

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    Are you here to get some information.......or to just argue ?
    I did NOT use the word "frequently".......so it does not fall into that category.
     
    #9 sam spade 2, Apr 29, 2020
  10. El Dobro

    El Dobro A Member

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    It may not be the problem, but it can happen. I know that VWs tend to have issues with the blades coming loose on water pumps.
     
    #10 El Dobro, Apr 29, 2020
  11. Air_Boss

    Air_Boss Senior Member

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    Here to understand the source and cause of an issue that I have never before heard of, if that's OK?
     
    #11 Air_Boss, Apr 29, 2020
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  12. sam spade 2

    sam spade 2 Senior Member

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    It is OK.....unless you persist in thinking you can always know WHY things happen.
    That is not always possible.

    The third time you asked "why" is slipping into the range of NOT OK.
     
    #12 sam spade 2, Apr 29, 2020
  13. mikefocke

    mikefocke Prius v Three 2012, Avalon 2011

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    The car is old. Parts fail over time. Bearings fail with use. Blades wobble and wear letting water around the blades.

    Though I like the thermostat as more probable. Test it in a pan over the stove where you can control the temperature.

    Why are the blades plastic. Because it is softer than the housing and you don't want a hard metal blade rubbing against the block because then even a new water pump doesn't fix the problem. Well known in some Porsche car forums because of postings from a well known shop owner who has seen the results of failures in both types of water pumps.
     
    #13 mikefocke, Apr 29, 2020
  14. Air_Boss

    Air_Boss Senior Member

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    Root Cause Analysis requires asking 'why', a lot.
     
    #14 Air_Boss, Apr 29, 2020
  15. CAITLIN FOLEY

    CAITLIN FOLEY New Member

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    Okay, maybe I can quell all the speculation.
    I started car. Turned on cabin heat to HI. It blows super hot. Then I disconnect the water pump which stops pushing hot coolant through heat exchange. I plug the water pump back in and within a minute, cabin heater is full blast HOT again. So to me, that rules out water pump as faulty. It's pushing hot fluid out the small thermostat outlet, but none out of the large radiator hose. This led me to suspect clogged radiator. So I flushed out the radiator with modified garden hose blowing both ways. It flows unimpeded both directions. Even when I pinch the small hose outlet to increase pressure to radiator, it still does not flow. There MUST be something blocking the flow between the radiator and the engine but there are so many little hoses and brass pipes up there, I can't figure out what the flow is. and I can't find a proper flowchart or diagram showing all the parts involved. If the cabin heater returns to the engine at a different location than the radiator then maybe that would help me diagnose. My next experiment is to run the garden hose into the radiator return hole and see if its blocked in the engine somehow. Maybe there's some extra thermostat or valve that isn't allowing the radiator fluid to enter. Worse case scenario, I can rig up the radiator output to Y into the heat exchange return because that is obviously working.
    That help out any questions?
    Ideas?
    Thanks
     
    #15 CAITLIN FOLEY, Apr 29, 2020
  16. lrisius

    lrisius Member

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    As several have said, the symptoms are classic for a thermostat not opening. The lack of heat going through the large radiator hose really makes me wonder about the thermostat. I know you changed it but it is possible that your new one is bad. I've never changed a thermostat on Prius yet, but I know on some cars it is possible to accidentally install them backwards. Mike's suggestion of pulling the thermostat and testing in pan on the stove is a good idea. I would recommend some additional testing to eliminate this possibility.
     
    #16 lrisius, Apr 30, 2020
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  17. fuzzy1

    fuzzy1 Senior Member

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    It is usually better to skip that person, and ask other people who respond much better to such questions.,
     
    #17 fuzzy1, Apr 30, 2020
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  18. CAITLIN FOLEY

    CAITLIN FOLEY New Member

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    Maybe I'll try thermostat on the stove idea. I did learn today, though, that the coolant flows INTO the thermostat and the water pump 'pulls' it from the radiator & other systems. Then it 'pushes' the coolant through the engine. I had it backwards in my mind. So I disconnected the lower radiator hose from thermostat and shoved my modified garden hose into the big thermostat hole. It pushed water all the way through the thermostat and water pump. Then through the engine and out the other side, then through the radiator, finally back out the lower radiator hose I had disconnected. The engine was still a little warm and so I was able to feel warm water coming through the radiator and hoses and out the other end. Then after a minute, the water cooled down as the engine did. Just sucks I cant drive around with my garden hose. :-/
     
    #18 CAITLIN FOLEY, May 1, 2020
    Last edited: May 1, 2020
  19. sam spade 2

    sam spade 2 Senior Member

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    OK Fuzzy, where are YOU with a better suggestion ?? :whistle:

    I still think the water pump might be bad......as in, it's capacity is way down due to something being broken inside.

    And just to further stir the pot.......does this model actually HAVE a thermostat ?
    Other discussions have indicated that some don't.......and I kind of assumed that maybe none of the did.
     
    #19 sam spade 2, May 1, 2020
  20. ChapmanF

    ChapmanF Senior Member

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    )sigh( Yes. Yes it does. It's built into the lower hose elbow for the 2ZR.

    The one discussion I remember seeing where somebody suggested otherwise, it involved taking off the hose elbow and then looking around where it came from trying to find a thermostat. :)
     
    #20 ChapmanF, May 1, 2020
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