high temp Thermostat?

Discussion in 'Gen 2 Prius Technical Discussion' started by Ianmeister, Jan 22, 2020.

  1. Ianmeister

    Ianmeister Active Member

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    hello all! So I've been thinking. my 2006 with 225K miles on it seems to struggle to get above 180F on engine coolant temp. Using torquepro app. The highest I've ever seen it is 186F on the freeway, heater off, no grille blocking. Winters are mild here near SF. I've found a 192F thermostat on Rockauto here:

    https://www.rockauto.com/en/moreinfo.php?pk=8205004&cc=1432870&jsn=2264

    I don't know the status of my existing one. Is there a benefit to upgrading to a higher temp unit? I do prefer to replace things before they leave me stranded. Any ideas?
     
  2. SFO

    SFO Senior Member

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    Can't see the benefit. Those temps are inline with what I've noticed.

    Replace if worried. You could also set an alarm in Torque as an 'early warning system', which saved me once or twice.
     
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  3. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    No.

    In fact, I would NOT call it an "upgrade."
     
  4. bisco

    bisco cookie crumbler

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    might increase combustion efficiency
     
  5. Ianmeister

    Ianmeister Active Member

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    hmm, mixed reviews then. I guess I'll leave it then.
     
  6. ChapmanF

    ChapmanF Senior Member

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    If the coolant isn't reaching the opening temperature of the original stat, a higher-temperature stat just won't be opening either.
     
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  7. Ianmeister

    Ianmeister Active Member

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    So update. I experimented with a full grille block and now the ICE rises to 190f quickly and stays there. My mpg average on the MFD has already gone up 1 full mpg in 50 miles of mixed traffic.
     
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  8. SFO

    SFO Senior Member

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    Be sure to also monitor the Inverter temps :whistle:
     
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  9. Classic Car Guy

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    How do you check the inverter temperature? Thanks,,,,
     
  10. SFO

    SFO Senior Member

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    The same way Ian is currently monitoring, using an OBD2 adapter and an app like Torque, Dr Prius, Techstream, etc.
     
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  11. Landon51

    Landon51 Member

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    is the inverter temp accessible they the odbc protocol or can it only be found on the canbus?

    Posted via the PriusChat mobile app.
     
  12. sam spade 2

    sam spade 2 Senior Member

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    Your grill blocking is a BAD idea.
    If the weather suddenly gets a lot warmer, your engine might overheat.

    It bypasses the real problem instead of fixing it.

    It sounds like your thermostat is stuck open.......or a previous owner removed it.
    I think you need a new one.
     
  13. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    Thermostats can fail in such a way that the engine runs too cold. The rubber gasket can fray/leak, and over time they can start opening too soon, closing too late.

    I experienced this with an Accord, years back: got a new thermostat, same spec's, suspended both in a post of water with thermometer and heated it. You could see the difference in performance. And the old thermostat's gasket was more brittle, the edge missing a few bits.
     
    #13 Mendel Leisk, Jan 24, 2020
    Last edited: Jan 24, 2020
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  14. VFerdman

    VFerdman Senior Member

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    It is silly to try and "outsmart" Toyota engineers that probably chose the thermostat operating temperature very carefully. Do you have the qualifications to be a Prius engine designer? If not, then stick to what Toyota engineers have come up with. Buy a new stock thermostat and replace whatever is in there. That will not hurt anything (unless you leave air bubbles in the system and do more harm than good).

    BTW, 1mpg over 50 miles is statistically insignificant, especially given the inaccuracy of the MFD MPG display.
     
  15. Classic Car Guy

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    Thank you Ray.. Planning to put a permanent or semi permanent gauge for at least the temperature. even though Ive done all the cooling system done, its better on knowing than not knowing when the surprise will come.

    As for the other guy on the thermostat. Try not to do any shortcuts. This is one of the most sensitive engine parts that requires a true specification. Just throw in a new original Toyota thermostat with original gasket and you're all set. Like what Mendel said the come in surprises. The worst surprise is the other way around. Stuck close. Ive seen this so many times on different cars and it heats up in seconds. The worst that a lot of people does is when it overheats they put water right away. It will blow up your head / head gasket or In your face:(. or both...
     
    #15 Classic Car Guy, Jan 25, 2020
    Last edited: Jan 25, 2020
  16. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    In case it's not clear: a thermostat that's got fraying gasket, and/or opening at too low a temp, too early in the warm-up process, leads to the coolant being too cold: flowing to the radiator too soon, too often, too much.

    With our Accord, I noticed this when driving to work to do overtime, early Saturday mornings. Hardly any other traffic, going the limit in cool weather on the freeway, made for ideal cooling conditions. A properly opening/closing thermostat would deal with this: shut off the flow of coolant to the radiator, off-and-on. But in my case it wasn't doing it's job, it was letting some coolant flow through the radiator all the time, and when I was pulling off at my exit I noticed the temp gauge was right down.

    Now with the modern, up-to-date Prius. we don't get a coolant gauge...
     
  17. ChapmanF

    ChapmanF Senior Member

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    As far as I know, about the only way there is for a thermostat to go stuck-closed is as a result of severe overheating that happens (at first) by some other cause.

    Short of that happening, an opening thermostat is pretty much physically guaranteed: that wax is going to expand, and the stat is going to open.

    The overheating-kills-your-thermostat scenario is just when something else makes the engine overheat, and it gets so hot the expanding thermostat wax busts right out. After that, the dead thermostat gives you repeat overheating even if you fix the original cause.

    So definitely check for a stuck-closed thermostat in the aftermath of any incident where the engine severely overheated. Otherwise, if nothing like that has happened, I don't believe a stuck-closed stat is at all likely out of the blue.
     
  18. Classic Car Guy

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    Not all old thermostat are fully operational with wax operation. Be mindful of the foreign object, low coolant mixture that can lead to oxide or water scales that will tend to make your moving parts inoperative. Either or in this case, the car is a miler, its recommendable to change the thermostat. I would.
    That being said, its Saturday and there is only one way to cut that thirst..:)
    Cheers brother!

    [​IMG]
     
    #18 Classic Car Guy, Jan 25, 2020
    Last edited: Jan 25, 2020
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