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Success! Replaced Water pump and Thermostat

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by alltherightpills, Jun 19, 2023.

  1. alltherightpills

    alltherightpills Junior Member

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    2011 Prius
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    III
    Today I swapped the water pump & thermostat (as preventative maintenance) on my 2011 w/ 166k.

    Not the most fun repair, but not terrible. I took off the passenger front wheel and pulled the cover back to expose the bottom bolt(s) - made that part much easier to accomplish.

    I use Torque Pro on my aftermarket head unit, so I've been able to watch my temps for the past 40k miles.

    Interesting observation: before the swap, my engine coolant temp averaged between 193-195, peaking at about 200 when I was pushing up a hill or something.

    Post-swap, the coolant is averaging 185, and only getting up to 192-193 when I'm pushing hard.

    I don't think 195 was damaging the engine, but I do like seeing a slightly lower average temp. Happy with the result!
     
    #1 alltherightpills, Jun 19, 2023
    ETC(SS), CR94, Brian1954 and 1 other person like this.
  2. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    Did you check how the old pump turned, compared to new?

    How did the old thermostat look, compared to new? Was there gasket fraying? One thing you can do is suspend both in a pot of water and bring the it up nearly to a boil, watch how they compare.
     
    #2 Mendel Leisk, Jun 19, 2023
  3. Brian1954

    Brian1954 Senior Member

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    Were the new water pump and thermostat Toyota OEM parts?

    The lower engine coolant temperatures may be due to the thermostat opening a little earlier and/or quicker than the old thermostat.

    Posted via the PriusChat mobile app.
     
    #3 Brian1954, Jun 19, 2023
  4. alltherightpills

    alltherightpills Junior Member

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    Location:
    St. Louis, MO
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    2011 Prius
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    III
    Old pump was still turning freely, but I pulled the impeller and could see a hairline crack starting to form. I think I got to this just in time.

    The thermostat looked alright and seemed to move alright, but had a bit of small debris buildup on the inside.

    Yep, OEM parts straight from the dealership. That seems like a logical explanation!
     
    #4 alltherightpills, Jun 19, 2023
    Mendel Leisk and CR94 like this.
  5. CR94

    CR94 Senior Member

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    Yes, that's interesting. Does anyone know whether Toyota lowered the thermostat opening temperature since 2011? My coolant temperature runs about the same as yours did with the old thermostat. That's hotter than expected, when the thermostat is supposedly specified to open at 82°C (180°F), as I recall.

    Of course, the engine temperature rapidly drops much lower when descending hills in fuel-cut mode in cool weather.
     
    #5 CR94, Jun 19, 2023
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