Need help! Gas engine overheating. Cannot resolve.

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Sergey K, Apr 1, 2019.

  1. 2012 Prius v wagon 3

    2012 Prius v wagon 3 Active Member

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    If you want to keep trying before giving up as others have perhaps wisely suggested, you might try to learn more about how the cooling system works until you can answer your own question and realize it's not a stupid design change at all.

    The car is still subject to the laws of physics, regardless of what the OBDII video game interface may make you think.
     
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  2. Shahzad Nayyar

    Shahzad Nayyar Junior Member

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    Hiw did u get water pump speed in obd fusion? I have searched but cant find?
    Posted via the PriusChat mobile app.
     
  3. PNP3

    PNP3 New Member

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    Can anyone advise if both radiator fan should blow cold air? I am having overheating issues under the heavy loads like driving uphill. So I checked the radiator fans. Both blow air towards the engine but one blows cold air and another one blows like a room temp / warm air. Is it normal?
     
  4. PriusGuy32

    PriusGuy32 Prius Driver Extraordinaire

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    The only times I have noticed this is when the head gasket goes bad, the cooling loop no longer can function normally as it doesn't pressurize (fully, or sometimes at all). The fans should blow toward the engine (fans don't ever blow outward toward the grille, that would be counterproductive to air coming in), and should be blowing hot air indicating a thermal exchange is occurring over the radiator fins. You, my friend, have bigger fish to fry here.
     
  5. TMR-JWAP

    TMR-JWAP Senior Member

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    First, I am not intimately familiar with the Gen 3 engine cooling system. I understand that the water pump is an electric motor driven assembly. It also must be variable speed if the ecu can detect overspeed conditions. So, it's probably safe to assume the pump speeds up/slows down depending on engine load/ecu signal? Low load...low rpm..low flow. High load...higher rpm...higher flow? If not, I guess it doesn't really matter very much. Same principles apply. Cooling systems need coolant flow, air flow and heat transfer. Let's assume the air flow and heat transfer portions are ok. Although it doesn't really matter, don't get distracted by fans. Fans are meaningless at highway speed. heck, they're mostly useless above about 20mph, as the cars forward speed becomes the main source of airflow. I guess it wouldn't hurt to verify the radiator isn't all gunked up with a bunch of roadkill or road debris. That would be too easy. That falls under air flow and heat transfer....

    For the coolant flow portion....
    Low flow conditions could easily be unaffected by a flow restriction. High flow conditions would be significantly affected. What is in the coolant path between the pump suction and the radiator? A water inlet assembly with a thermostat?

    Most thermostat assemblies I've seen have a bypass that allows the water pump to move a small amount of coolant even when the thermostat is closed. This could easily explain why the engine is ok under low load conditions. Under high load, the engine would overheat due to inadequate flow. Perhaps, the simplest answer is the thermostat is stuck shut?
     
    #125 TMR-JWAP, Nov 24, 2020
    Last edited: Nov 24, 2020
  6. PNP3

    PNP3 New Member

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    I checked the outside of radiator and found it clean. I noticed one thing that when it is overheating, the coolant level in reservoir goes up and overflows. So from past two days, I was trying to get air out but raising the tank, opening bleeder valve etc but today my water pump (this is third one) gave up. Does anyone has experience this? I am having this issues after I swapped the engine. I have Gen 4 engine in Gen 3 but I am just blowing off this water pumps one after another. Please help!
     
  7. TMR-JWAP

    TMR-JWAP Senior Member

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    Does the Gen4 have the same water pump setup as the Gen 3?

    It's 30 bucks for a thermostat/water inlet assembly....why not just replace it and see if the problem goes away?
     
  8. TMR-JWAP

    TMR-JWAP Senior Member

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    This is a pretty normal thing for an over heating engine. You have a flow problem. Whether it's a restriction in the suction side, discharge side, or just jacked up hose routing, it's a flow problem. Start verifying the flowpath is correct. Verify there isn't something causing the pump to just circulate coolant without it passing through the radiator. Just spend 30 bucks and replace the thermostat assembly.
     
  9. PNP3

    PNP3 New Member

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    I have replaced the old one with new thermostat so do you think it could be radiator? I see the coolant overflowing as car overheats
     
  10. jzchen

    jzchen Senior Member

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    I have an itchy feeling it's flowing the wrong direction vs circumventing the radiator. Suggest removing the thermostat and putting a jumper tube in it's place. (If possible).

    moto g(7) power ?
     
  11. PNP3

    PNP3 New Member

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    what is jumper tube?
     
  12. TMR-JWAP

    TMR-JWAP Senior Member

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    I wish I was more familiar with the Gen 4, but I'm about tapped out on suggestions. I did find a ZR engine series coolant flow path diagram on line. It's not specific to the hybrid model, but it's the same engine family, so I would suspect the path is similar. Maybe it can help you trace the coolant path.

    ZR coolant flowpath.jpg
     
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  13. PNP3

    PNP3 New Member

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    Thank you. When I open the bleeder valve at time of coolant reservoir overflow, coolant level goes down in coolant reservoir and it stops overflowing. Does it mean overheating and coolant overflow is due to air?
     
  14. ASRDogman

    ASRDogman Senior Member

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    You could have a blow head gasket. Did you replace the gasket? Or just install the engine?
    Exhaust is blowing into the coolant causing it to overflow. I had a Ford Aerostar that did that.
     
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  15. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. Check engine cylinder compression to make sure the installed engine is basically OK.
    2. Remove the engine thermostat and suspend in hot water to make sure the thermostat opens at 176 degrees to 183 degrees F. At 203 degrees F the thermostat should be open 0.4 - 0.55 inches.
    3. Are you using the correct Toyota engine coolant pump - or some cheap aftermarket substitute?
    4. While the engine coolant pump is operational, does the engine still overheat?
    5. How long has the G4 engine been installed in the G3 Prius and how many miles have been logged by that engine; and has it ever worked correctly since the installation?
     
  16. PNP3

    PNP3 New Member

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    @ASRDogman
    I replaced it with new engine. Overflow of coolant doesn't happen when car is not under the load.
    @Patrick Wong
    1. Compression test was done before replacing the engine
    2. Thermostat was tested outside in boiling water. I have two and both opened up when I tested before replacing.
    3. I am using AISIN Water Pump (WPT-205)
    4. It didn't overheat while driving local but when It was under load (highway speed and uphill), it started overheating. When it overheated, I checked the coolant level in reservoir and found coolant overflowing. I observed this pattern after installing two new AISIN water pumps after first one failed.
    5. Engine has worked correctly after installation but only issue has been overheating. It is same pattern as mentioned above. I have tried to open bleeder valve when it overheats and coolant overflows. When I open bleeder valve, coolant level goes down and I see air and coolant comes out of bleeder valve. When I close it after seeing steady flow of coolant from bleeder valve, it still does the same as mentioned above in 4.
     
  17. Patrick Wong

    Patrick Wong DIY Enthusiast

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    It is very strange that you report air remaining in the engine coolant system which is coming out of the bleeder valve, and I am wondering if substantial air still remains. A few questions:

    1. The G3 engine coolant capacity is 7.7 US quarts. Do you recall how much coolant you added when you first installed the G4 engine?
    2. Does the cabin heater work OK, or do you hear air bubbling in the heater core? (That is evidence that more air remains in the system.)
    3. As you run the engine with the car sitting on your driveway, can you get the engine sufficiently hot so that the thermostat is open? (At that point you should feel hot coolant at one radiator hose, and cooler coolant at the other radiator hose. This will show that the thermostat is opening as the coolant gets hot.)
     
  18. PNP3

    PNP3 New Member

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    @Patrick Wong
    1. I added more than a gallon. I used one whole gallon and about .25 gallon more.
    2. Cabin heater worked fine when I was driving locally. But it started acting up when it started overheating under the load. I heard air noise very first time when I installed pump but then it went away after I bled the air.
    3. In driveway during air bleed, I was not feeling the thick hose that connects thermostat and radiator. But after squeezing it for few mins, it started getting hot. I have yet to check the other hose that goes from radiator towards engine block.

    Plus - During my last two water pump I noticed that heat worked fine till engine start overheating and overheating started only under load. During driving locally, everything just worked fine. But in both instances, pump gave up after it started overheating. Does it mean something goes wrong in the pump in few minutes of overheating? Do you think I should buy one from toyota and not from anyone else who sells this AISIN water pumps?
     
  19. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I think that the pump fails, which then causes the engine to overheat. If you are actually getting an Aisin water pump, that should provide an original equipment quality level. If you somehow are getting counterfeit merchandise, then who knows.

    Are you using a quality import parts supplier; or some unknown on eBay? What did you pay for the pump?

    As one data point, Longo Toyota is selling the G3 electric coolant pump for $201.
    2010-2019 Toyota Water Pump 161A0-29015 | Longo Toyota Parts

    Same price for the G4 pump:
    2016-2020 Toyota Water Pump 161A0-39035 | Longo Toyota Parts
     
    #139 Patrick Wong, Nov 27, 2020
    Last edited: Nov 27, 2020
  20. PNP3

    PNP3 New Member

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