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Water Temp beginning to wander, fan issue?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by navguy12, Oct 22, 2012.

  1. navguy12

    navguy12 Member

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    Greetings all:

    Situation: I have driven my 2008 Prius over 20,000 km's since purchase 9 months ago. Scangauge II used as, among other things, coolant temp monitor.

    For all my time driving this car (winter, spring, summer, fall, AC-on, AC-off, city, highway), after initial warm-up, the water temp has stayed at 85C (Scangauge II indicated).

    Last 10 days or so, temp is swinging, to climb and hover at 90-95C, then will settle back down at 83C, then up to 85C, etc.

    When AC turned on, both electrical fans (radiator) come on, so radiator fans do work. Coolant level is at correct points (temp low, lower line, temp hot, upper line of reservoir).

    At 95C, the rad fan will not click on. Do I have an issue?

    I called the dealer and explained the above. He doesn't know the temp that the fan should come on at. Does anyone know that spec? Do I have a (fan controller) sensor (temp or pressure) issue?

    Or is it a sticky thermostat?

    Please advise.

    Thanks

    Cheers

    Mike
     
    #1 navguy12, Oct 22, 2012
  2. jadziasman

    jadziasman Prius owner emeritus

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    Service manual says it's one of the following if the cooling fan doesn't run above 93°C with the A/C off.

    Check the fuses, cooling fan relay, ECM, cooling fan, and engine coolant temperature sensor.
     
    #2 jadziasman, Oct 22, 2012
    xs650 likes this.
  3. navguy12

    navguy12 Member

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    jadziasman, thanks.

    Just buying an Adobe version of the '08 shop manual now. Will give me something to organize my troubleshooting with. Car has Toyota warranty, just want to narrow the diagnostic time prior to any dealership visit.

    One other question: what temp will trip the idiot light on the dash?

    Thanks

    Cheers

    Mike
     
    #3 navguy12, Oct 22, 2012
  4. northwichita

    northwichita .

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    I vote for a failing thermostat,cheap and not too hard to replace.
    I recall having the engine temp light come on at 248 F when driving the car after an incomplete coolant change.
    The engine is still running many months later, so it must not have hurt it (I did stop asap.)
     
    #4 northwichita, Oct 22, 2012
  5. navguy12

    navguy12 Member

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    northwichita: Thanks. My instinct is telling me that. But at 95C, the radiator fan will not trip on.......?
     
    #5 navguy12, Oct 22, 2012
  6. HaroldW

    HaroldW Active Member

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    Sticking thermostat. H
     
    #6 HaroldW, Oct 22, 2012
  7. jadziasman

    jadziasman Prius owner emeritus

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    Couldn't find the temperature the warning light goes on at on the MFD in the service manual or the owners manual.

    The ECM triggers a DTC when the temperature reaches 140°C but that's considered to be a coolant temperature sensor malfunction (short to ground). The upper limit for the sensor itself is 140°C apparently - the resistance at that temperature is essentially 0 ohms.
     
    #7 jadziasman, Oct 22, 2012
  8. navguy12

    navguy12 Member

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    Harold, thanks, long time no hear :).

    I'll live with the symptom in the short term until I'm satisfied the cooling system fan will turn on when called for.

    To R&R the thermostat means to R&R the coolant. Using the "Without Cooling System Bleed Tool" technique, one must still force the electric coolant pump on for 30 seconds and clear any set codes after the procedure.

    I don't have the special Toyota scan tool and my 10 year old OBD II tool does not seem to talk to this car......
     
    #8 navguy12, Oct 22, 2012
  9. navguy12

    navguy12 Member

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    OK, 140C, thanks!
     
    #9 navguy12, Oct 22, 2012
  10. JimN

    JimN Let the games begin!

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    95C (203F) is a little high. My coolant temp runs about 87C (190F) with the grill blocked. I rarely see a temp as high as yours. Now everyone knows why we run with a ScanGauge. I don't believe this needs immediate attention especially with falling temps but I'd get the car into the garage sooner rather than later.
     
    #10 JimN, Oct 22, 2012
  11. fuzzy1

    fuzzy1 Senior Member

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    At what temperature does your fan turn on, if you have found that point yet?

    I know mine is a different model series (Gen3 2010, now 2012), but ...

    When the temperature is stable, not cooling off from lack of heat, I usually see 192F (89C). This car runs warmer than my non-hybrid (184F, 84C).

    When it starts rising, with grill blocked, it usually peaks at 202F (94C), sometimes 204F (95C) then falls, which I believe is the fan turning on. When this happens, I go remove another strip of grill block.
     
    #11 fuzzy1, Oct 22, 2012
  12. navguy12

    navguy12 Member

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    Jim, thanks. Mine used to run at 85C, blocked, not blocked, etc. Currently not blocked and temps here about 15C. I know it will need formal attention, just doing my sanity check here before it goes to the dealer (knowing me, I want this dealt with sooner than later.
    Fuzzy, thanks. I can't seem to get my fan to come on and earlier in this thread was shop manual info stating fan should run at temps above 93C. So I have to confirm my fan, in fact, will come on at 94C and above (runs with AC on).
     
    #12 navguy12, Oct 22, 2012
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