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Persistent high temp light

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by animartis, Jul 19, 2011.

  1. animartis

    animartis Junior Member

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    Hello all,

    I have a 2005 Prius with 234K. Over the last week, the red triangle has been coming on along with "problem", followed by the high temp light. I originally checked coolant levels then took it into Toyota. Here was the diagnosis:
    ---
    Found two low voltages codes stored
    Replaced thermostat

    Notes: Temp light on MDU does indicate malfunction. Low battery may have erased codes. Found the cooling system low on coolant. Pressure tested system (no leaks seen at this time), tech noted thermostat stuck closed. Replaced thermostat and refilled cooling system.
    ---
    Now on the 45 min commute home the error did not re-occur, but it did happen the next day. I took it back into Toyota and this time there were no errors stored. I also told them that the heater wasn't blowing hot air but when they tested the heater it worked fine. They told me to document any time it happened to see if I could find a common cause.

    It has been two days and now it is happening constantly. Today going up a long hill that I drive every day, the battery completely drained and I had to go up the hill at 38 miles an hour. The heater still does not work for me.

    I'm at a loss and am looking for any advice.

    Thanks
     
    #1 animartis, Jul 19, 2011
  2. cwerdna

    cwerdna Senior Member

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    What were the codes? Has the inverter pump been changed? When was the last time the 12 volt battery was changed?
     
    #2 cwerdna, Jul 19, 2011
  3. animartis

    animartis Junior Member

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    Unfortunately, the invoice does not have the codes listed and I did not think to ask. The inverter pump has not been changed. (Wouldn't the dealer check this, or is that a bad assumption?). I don't believe the 12-volt battery has been changed but the last time I did the OSD check of the battery it was with specs. Sorry I don't have better information.
     
    #3 animartis, Jul 19, 2011
  4. efusco

    efusco Moderator Emeritus
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    your inverter coolant pump should be eligible for replacement under the recall--that's the first place I'd look.
     
    #4 efusco, Jul 19, 2011
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. Replace the 12V battery now. If it hasn't died yet it will, very soon.

    2. If you are still seeing an overheating icon, then as already suggested, the inverter coolant pump is the likely suspect causing your driveability problems. It is likely that the inverter is overheating, not the engine.

    3. Do you hear air gurgling around when you are running the cabin heater? If so, set the cabin temp to MAX HEAT (or the highest temp possible), set the cabin fan speed to the fastest speed, and floor the accelerator pedal while the car is READY and in P, to rev up the engine and hopefully move coolant through the system, getting rid of the air bubbles. Do this for around 15-20 minutes or until you stop hearing air gurgling around.

    If that doesn't work, I suggest that you demonstrate to the dealer service writer that the cabin heater is not working. If you can show the problem to him/her, then he/she can better explain to the tech what your concern is. Good luck.
     
    #5 Patrick Wong, Jul 19, 2011
  6. seilerts

    seilerts Battery Curmudgeon

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    Low coolant + no heat = airlock. This means that there is air at the engine water pump impeller, so coolant will not circulate, so the engine will overheat, while the heater will not work at all. If the tech noticed a low coolant level, it should have been bled, rather than simply filled. It is more complicated than the typical car, due to the coolant heat storage tank ("thermos").

    Have you had the engine water pump replaced before? If not, you probably have a very slow coolant leak, which may not reveal itself on a pressure test. This is the most common cause of low coolant on Toyotas.
     
    #6 seilerts, Jul 19, 2011
  7. cwerdna

    cwerdna Senior Member

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    #7 cwerdna, Jul 20, 2011
  8. Joe 26

    Joe 26 Member

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    The lack of cabin heat is a big clue. Follow Patrick's suggestions to purge the air from the engine cooling system.
     
    #8 Joe 26, Jul 20, 2011
  9. animartis

    animartis Junior Member

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    Sorry it has taken so long to respond. I just wanted to thank you all for your responses and advice. To give a quick update:

    I did not realize the inverter pump and the recalled water pump were one in the same. Yes, that has been replaced. Also, I purchased a new 12V battery but have not installed it yet because the check engine light came on for the first time during this whole ordeal. Since I'm assuming that light will be associated with an actual code, I've taken it into Toyota once again and am currently awaiting their diagnosis.

    I will post again once the results are in. Thanks again.
     
    #9 animartis, Jul 23, 2011
  10. niphonk98

    niphonk98 Junior Member

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    I got the air gurgling when I take off. I try to get rid the air bubbles in the system but It's did work. How can I do?
     
    #10 niphonk98, Aug 1, 2016
  11. andrewclaus

    andrewclaus Active Member

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    You may want to search for Youtube videos on this. The correct procedure involves running the CHRS pump and using the upper radiator bleed valve. Be careful working with coolant, and always work on a COLD radiator. These are specialized Prius techniques, and even many dealer mechanics don't get it right either.
     
    #11 andrewclaus, Aug 1, 2016
  12. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. Check the engine coolant level in the radiator and replenish. The fluid level must be at the top of the radiator neck.
    2. Rev up the engine for an extended period, as discussed in my post #5 above.
    3. See my posts #22 and #42, as well as the surrounding discussion, here:
    Changing engine coolant | Page 2 | PriusChat
     
    #12 Patrick Wong, Aug 1, 2016
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