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ICE coolant tank overflowing/check hybrid system light

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Jiwanowski, Sep 21, 2018.

  1. Jiwanowski

    Jiwanowski Junior Member

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    Hello guys!

    So I need some help troubleshooting my Gen3 Prius... I replaced the water pump a few months ago and just did a thorough cleaning of the EGR cooler, throttle body, intake manifold, replaced the gaskets, and drained and refilled the coolant. I followed NutzAboutBolts video instructions on refilling the reservoir and letting the car run in maintenance mode to get the air out of the system. The car ran for about 10 minutes then cut itself off and spewed coolant out the top of the reservoir. Now the “check hybrid system” message is displayed and the car won’t turn back on. Any thoughts on what could be wrong with it? I’m getting frustrated with it and really don’t have he money to drop at the dealership...
     
    #1 Jiwanowski, Sep 21, 2018
  2. tankyuong

    tankyuong Senior Member

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    Hopefully your engine didn’t overheat by having air in your system
     
    #2 tankyuong, Sep 21, 2018
  3. Jiwanowski

    Jiwanowski Junior Member

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    That is one concern but I have noticed that Toyota did a really good job with failsafes in these cars. They seem to have worked safety switches into the design so it’s harder for people to destroy the engine or hybrid systems. I’m questioning if the thermostat seized and is restricting the coolant from passing through.
     
    #3 Jiwanowski, Sep 21, 2018
  4. bisco

    bisco cookie crumbler

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    very possible, perhaps torque or some other reader will give you coolant temp
     
    #4 bisco, Sep 21, 2018
  5. Raytheeagle

    Raytheeagle Senior Member

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    You replaced the water pump and didn’t do the thermostat?

    That’s the usual pairing and puts them both on the same schedule;).

    I did our 2010’s water polo mo and thermostat at 173 k miles as preventative maintenance.

    Are there any codes to read or dash lights displayed?

    Good luck and keep us posted (y).
     
    #5 Raytheeagle, Sep 22, 2018
  6. Jiwanowski

    Jiwanowski Junior Member

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    I thought about doing the thermostat but at the time money was tight and I’ve never had one go bad so I let it slide. It’s only been 10k miles since I did the water pump. I probably should have figured that the thermostat was seizing up since the water pump was but it makes more sense now.

    I’ve spent a lot of time thinking about the issue and my conclusion is that coolant isn’t flowing past the thermostat. I was only able to put in a little less than a gallon of coolant and the reservoir never drained any. I’m thinking that it filled the radiator and a couple hoses but not the engine, heater core, or egr cooler. It seems like the coolant hit a blockage (thermostat) expanded and backflowed back into the reservoir and out the spout. Makes sense in my head anyway. I’ll replace the thermostat and see what happens next. Btw I’m at 215k and this is the first time any of these parts have been replaced. I’d been sticking with oil changes and spark plugs until I started having these issues...

    I do have to ask, has anyone seen the “check hybrid system” message from the engine overheating?
     
    #6 Jiwanowski, Sep 22, 2018
    Last edited: Sep 22, 2018
  7. bisco

    bisco cookie crumbler

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    you should run through the air bleed process just to make sure.
     
    #7 bisco, Sep 22, 2018
  8. Jiwanowski

    Jiwanowski Junior Member

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    That’s what I was doing when the car shut off and overflowed coolant.
     
    #8 Jiwanowski, Sep 22, 2018
  9. ChapmanF

    ChapmanF Senior Member

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    With Techstream you can just tell the electric water pump to run, even just in IG-ON with the engine itself stopped. That might be helpful for making sure the coolant loop is properly filled and bled.

    It's really hard for a thermostat to die of natural causes ... it's just too dead-simple and reliable. If it were to rust up and seize, that would tend to put it in a fail-open state, with low engine temps and slow warm-up resulting. The thermostat opens through the thermal expansion of a wax, and no rusty stiction is going to stand in its way.

    However, there is one way for a thermostat to be killed: if the engine severely overheats (maybe for some other reason at first), that's likely to kill the thermostat. It opens as far as it can, then the wax keeps expanding and bursts its containment. Then you do have a thermostat that won't open when it should, and will lead to repeat overheating.

    So, the recommendation to replace the thermostat along with the water pump is a sound one, if your reason for replacing the pump was that it failed and the engine overheated.

    -Chap
     
    #9 ChapmanF, Sep 22, 2018
  10. Jiwanowski

    Jiwanowski Junior Member

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    I placed an order for a mini vci cable and the techstream software. It should be here by next weekend. I’ll update once I’ve had a chance to see what the readings are.
     
    #10 Jiwanowski, Sep 23, 2018
    Raytheeagle likes this.
  11. Jiwanowski

    Jiwanowski Junior Member

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    So the mini-VCI showed up early! I just checked it out and you can hear the ICE water pump running but techstream showed an P261B Engine Coolant Pump "B" Control Malfunction. Guess I need to figure out how to claim a DOA on that one... unless someone has a suggestion before trying another water pump. Also have a B1503 Exhaust Heat Management Warning Detected... Haven't looked into that one yet.
     
    #11 Jiwanowski, Sep 27, 2018
    Last edited: Sep 27, 2018
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