Coolant temperature sensor blues

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Wrecit, Jul 18, 2026 at 7:47 PM.

  1. Wrecit

    Wrecit Active Member

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    I hope there is a special level of hell dedicated to the engineers that designed the engine bay on the 2010 Prius.

    Coolant temperature sensor went on my wife’s DoorDash car. A $28 part and should be a 20 minute job.

    Have half the engine bay dismantled and still can’t get leverage on the safety lock button on the plug end to get the frakin thing to disengage so I can get a socket on it and I only have the good non slip crows foot wrenches so I can’t even slip a crows foot wrench on to turn and expose the button.

    May a million sand fleas from a leapers camel infest their crotches for eternity

    anyone got any tricks on pushing the release button when it’s at 6 o’clock and crusty from 16 years of working? Can’t find my grinder or else I would cut the “safety tabs” off my 3/4 crows foot and just break it loose to better access
     
    #1 Wrecit, Jul 18, 2026 at 7:47 PM
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  2. PriusCamper

    PriusCamper Senior Member

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    I'm just get used to a really cheap 2010 with similar thoughts... Every time I look into it I find more stuff that needs to be fixed. So different than Gen2 Prius that hardly has anything wrong with it.
     
    #2 PriusCamper, Jul 19, 2026 at 1:42 AM
  3. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Is there more than one sensor? Just browsing the Repair Manual, is it this one, in the junction with white (air-release) cap on top, at a hose juncture above the EGR components:

    upload_2026-7-19_8-57-1.png

    For another bone-head access issue, I'd nominate the inverter coolant pump: short of some metalwork, you need to remove the effing inverter to get to it.
     

    Attached Files:

    #3 Mendel Leisk, Jul 19, 2026 at 11:57 AM
  4. rjparker

    rjparker Tu Humilde Sirviente

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    There are two, your pic is downstream of the exhaust heat recirc system ehrs flow and sensors partial.jpeg


    This one is at the large engine to radiator hose
    Location of Engine block coolant temp.jpeg
     
    #4 rjparker, Jul 19, 2026 at 11:58 AM
    Last edited: Jul 19, 2026 at 12:04 PM
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  5. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Thanks, yeah, I was thinking as much.
     
    #5 Mendel Leisk, Jul 19, 2026 at 12:00 PM
    Last edited: Jul 19, 2026 at 12:08 PM
  6. rjparker

    rjparker Tu Humilde Sirviente

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    You can buy a connector removal tool or a set that holds the clip down while you wiggle it off.

    IMG_2159.jpeg
     
    #6 rjparker, Jul 19, 2026 at 12:10 PM
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  7. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Might be a bear getting the handles down there, so much in the way. I “think” this is it:

    IMG_4389.jpeg

    (For reference, junction of EGR valve/cooer just above)
     
    #7 Mendel Leisk, Jul 20, 2026 at 2:13 PM
  8. rjparker

    rjparker Tu Humilde Sirviente

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    Except he has
    The trick is to hold it down while wiggling it side to side. It will quickly release with little damage except to your hand if you are forcing it when it gives.
     
    #8 rjparker, Jul 20, 2026 at 3:05 PM
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  9. Wrecit

    Wrecit Active Member

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    ended up dropping $30 at autozone for the removal pliers. Took bolts out of the inverter coolant tank and the wife used the pliers and had it off in 10 seconds. At 53 she wanted to learn auto mechanics and every job we do she embarrasses me by removing stuff I loosened for an hour lol
     
    #9 Wrecit, Jul 21, 2026 at 9:28 PM
  10. Wrecit

    Wrecit Active Member

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    Baby (our second gen) is a dream to work on compared to tink (our third gen) have you changed the coils and plugs on your gen 3 yet lol. It was so thoughtful of the engineers to make sure you make sure to inspect (remove) the entire wiper rack to do what should be a 10 minute plug change
     
    #10 Wrecit, Jul 21, 2026 at 9:32 PM
  11. rjparker

    rjparker Tu Humilde Sirviente

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    The engineers were giving you wiper assembly muscle memory so its only 15 minutes of your brake booster, egr cooler or head gasket job.
     
    #11 rjparker, Jul 21, 2026 at 9:36 PM
  12. Mendel Leisk

    Mendel Leisk MMX GEN III

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    I’ve still got one cowl bolt I could not find a location for. The other dozen or so should suffice.
     
    #12 Mendel Leisk, Jul 22, 2026 at 8:21 AM
  13. ChapmanF

    ChapmanF Senior Member

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    Just keep it around for the next time you have the cowl off. You'll probably spot where it goes then,
     
    #13 ChapmanF, Jul 22, 2026 at 9:28 AM
  14. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Oh, I have a Prius box. Put labelled twist-ties on such. Also contains the EGR cooler lower bracket nut/stud combo, an extra PCV hose (current one cut for oil catch cans), extra O-rings (for aforementioned OCC's), extra aftermarket socket-head cap screws for the EGR valve cap, teeny packs of anti-seize, extra plastic fasteners, you name it.

    Still, when reinstalling the cowl, I looked it over exhaustively, could not find a missing bolt location. It's a distinctive bolt too, galvanized IIRC. Ah well...
     
    #14 Mendel Leisk, Jul 22, 2026 at 11:32 AM
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