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Intermittent thermometer (beep, red triangle of death, problem, thermometer)

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Marcilla Smith, May 25, 2018.

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  1. Mendel Leisk

    Mendel Leisk EGR Fanatic

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    The '80's Accord with the opening-too-soon thermostat also had a quaint device; the Prius is too advanced and cool for this: a coolant temp gauge.

    Driving to work on an overtime saturday, hardly any other traffic, as I was pulling off at my exit I was suprised to see the temp gauge was right down at the bottom. Easy running on the freeway, cool morning, the thermostat opening too soon, and staying open too long, was allowing free-flow of coolant out to the radiator in a high speed low temp air stream.

    Hey Toyota, bring back a simple coolant gauge, please?
     
    #21 Mendel Leisk, May 26, 2018
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  2. Marcilla Smith

    Marcilla Smith Active Member

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    I appreciate all of the assistance. Sometimes it's a good idea to get "eyes on the objective," too.

    Looking under the hood to see if I thought I could replace the thermostat myself on this holiday weekend (when so many places are closed, but I still need to get to work this afternoon), I happened to notice that one and a half screws have worked themselves out of the "fan" belt pulley, and the belt is hanging on a piece of trim under the motor.

    While I'm no automotive engineer, I suspect this may be related to the overheating issue
     
    #22 Marcilla Smith, May 27, 2018
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  3. Raytheeagle

    Raytheeagle Senior Member

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    I think you found your problem;).

    Now getting it fixed will be a challenge as you note this weekend:(.

    Sounds like a call to the mechanic will be in order early next week:).

    Enjoy your holiday weekend(y).
     
    #23 Raytheeagle, May 27, 2018
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  4. JC91006

    JC91006 Senior Member

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    I would say this is the most likely cause of the overheating issue. Not the thermostat
     
    #24 JC91006, May 27, 2018
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  5. ChapmanF

    ChapmanF Senior Member

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    I agree that the root cause analysis seems to be completed. :)

    By the same token, with temperatures known to have reached 250 F because of that root cause, I would strongly consider picking up a thermostat as well, because, as commented upthread, extreme temperature from some other cause is the main thing that can turn a working thermostat into an ex-thermostat, which can leave you with continued overheating even after correcting the original cause.

    Which pulley had the loose screws? The one on the crankshaft or the one on the water pump? (I was going to say "or the one on the tensioner?" but I think that one just has one big bolt and nut through the middle.)

    -Chap
     
    #25 ChapmanF, May 27, 2018
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  6. Marcilla Smith

    Marcilla Smith Active Member

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    Thanks to y'all's encouragement, I think I'm finally in the clear for now!

    The pulley on the water pump is the one that had the loose screws. I say "had," since the missing one has been replaced, and they are all tightened, now.

    I drove it to work - several miles on I-40 - and with the a/c, no warnings came on. On the way home, I connected the TS first, and the coolant temp rose to the 185 - 190 F range and stayed there on the interstate, on surface streets, and while idling.

    Apparently, there's something about having the serpentine belt connecting the engine pulley and the water pump pulley, rather than resting on the plastic underbody panel, which helps prevent overheating.

    Incidentally, the last car I had that I worked on myself was an e30 BMW. Despite rumours to the contrary, it had a remarkably consistent and straightforward repair procedure: 1) disassemble the entire vehicle, 2) replace the appropriate part, 3) reassemble vehicle, 4) gather all remaining parts, 5) disassemble entire vehicle, 6) reinstall parts collected in step 4, 7) reassemble vehicle, 8) repeat steps 4-7 until ownership of vehicle is transferred.

    Which is to say: "I'm starting to see why people refer to this car as 'an erector set,'" and "blessings on you, Toyota!"
     
    #26 Marcilla Smith, May 27, 2018
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  7. ChapmanF

    ChapmanF Senior Member

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    Can't ask for any better than that. Good show!

    Toyota may need to know about that ... I noticed in the third gen, they omitted the belt completely! :)

    Yeah, I like most of their decisions for serviceability. Most... Yours is easier, third gen got pretty annoying for oil and spark plug changes....

    -Chap
     
    #27 ChapmanF, May 27, 2018
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  8. tandomwolf

    tandomwolf New Member

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    ***I had the same problem and after having the coolant system Purge and knowing it was not the inverter pump and they didn't catch it at the shop but my serpentine belt was broken and that was causing this problem because it was allowing the gasoline engine to overheat. As soon as it broke within 15 seconds it began doing this and did not stop until we got it changed which also might I was not easy to do because the tensioner pulley was almost impossible to get to move but we finally did and we are problem free. So as simple as it sounds you may want to check your belts the serpentine belt on the 2004 Prius is on the left if you open the hood and look down in there it will be near the water pump
     
    #28 tandomwolf, Dec 29, 2022
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