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High temp warning light goes on and off

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by TheBeholder1805, Jan 16, 2014.

  1. TheBeholder1805

    TheBeholder1805 Junior Member

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    I have a 2006 Prius with 176k miles on it. I drive it about 65 miles each way to work every day. If I really baby the throttle, no warning lights ever come on, and the heat will take about 45 minutes to kick in. If I use the gas a little more aggressively, the heat will start working after about 30 minutes when I get on the freeway and speed up, BUT the high temperature warning light will intermittently come on. First, the red triangle Warning light will come on, followed by "PROBLEM" on the display followed by a red temperature indicator. Typically it flickers off after just a few seconds, but sometimes the temp light stays on for longer, maybe 30 seconds or a minute before it shuts off. Then it continues to go on and off every few minutes for as long as I'm on the freeway. It doesn't seem to be directly related to when I hit the gas. I have checked the coolant level and it looks fine. I bought the car back around 2010 when it had just received it's 100k mile maintenance and they had also just replaced the water pump. I haven't looked at the OBD-II codes, if there are any. I have never replaced the 12v battery. The lights are pretty annoying/alarming and I'm not sure if it's "normal" for the heat to take 30-45 minutes to come on. Any help would be appreciated! Maybe the 12v battery or the inverter pump need to be replaced? Thanks everybody!
     
    #1 TheBeholder1805, Jan 16, 2014
  2. JC91006

    JC91006 Senior Member

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    Did you check the coolant level in the radiator or only at the coolant reservoir? You are suppose to do a coolant change at 100k and every 50k after. I would try to replace the coolant and do a complete flush and see where it goes from there. You might want to consider replacing the thermostat to make sure that's not the cause.

    While you're at it, double check that the coolant pump is not leaking. The electric coolant pump was replaced under recall, the ICE coolant pump seems to develop a leak on many of the Prius cars.
     
    #2 JC91006, Jan 16, 2014
  3. TheBeholder1805

    TheBeholder1805 Junior Member

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    I only checked the coolant level at the reservoir.
     
    #3 TheBeholder1805, Jan 16, 2014
  4. dorunron

    dorunron Senior Member

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    It sounds like the coolant level is low. Check it by removing the radiator cap which is hidden underneath the black plastic shroud. Chances are there is a air pocket and that the system is not full of coolant. Happens at times when water pumps are changed. Prius is finicky about this and can be tricky to refill and bleed all of the air out. Make sure you only remove the cap when the engine is cold. Hot coolant is under pressure and can scald you.

    Don't go by the overflow bottle, check it under the radiator cap. It should be full to the neck.

    There are instructions here on Prius Chat on changing coolant. Details will be found there on how to refill and bleed the air out of the system. Once you get it full and bled, the heater should start working normally and you should see no more warning lights.

    I would suggest that you take care of this. The longer you drive it in it's present condition, the greater the risk of overheating the engine and causing costly damage to it.
     
    #4 dorunron, Jan 16, 2014
  5. dorunron

    dorunron Senior Member

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    Refer to this page for instructions on draining, refilling, and bleeding of the coolant system. Study post #22 and #42 for the information you need to refill and bleed your system.

    Changing engine coolant | Page 2 | PriusChat

    Follow that and you should be good to go.

    Best of luck to you.
     
    #5 dorunron, Jan 16, 2014
  6. nh7o

    nh7o Off grid since 1980

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    The fact that the cabin heat is delayed sounds like the system may not be properly purged of air. This is notoriously difficult to do with the engine coolant loop. If possible get the codes read and see if the coolant control valve is acting up.
     
    #6 nh7o, Jan 16, 2014
  7. TheBeholder1805

    TheBeholder1805 Junior Member

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    That did it! Took it to the dealer and had them flush and refill the coolant. They suggested replacing the thermostat but I declined and had them flush the system to save myself a trip later. Ran me $200 but the light no longer shows up and the heat is perfect now! Thanks for the help guys (and gals if the case may be)!
     
    #7 TheBeholder1805, Jan 27, 2014
  8. nh7o

    nh7o Off grid since 1980

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    Glad to hear it. The question is then how did the system get air inside? Perhaps it was never properly purged at some time in the past. Or else there might be a small leak which will admit air after the system cools. Then engine water pump is one thing to check.
     
    #8 nh7o, Jan 27, 2014
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