Need help! Gas engine overheating. Cannot resolve.

ChapmanF · Mar 27, 2022

That hose loop and that second temperature sensor are for the exhaust heat recirculation system, which I do not think is used in all market regions.

I wonder if it is present in Lithuania. Does the exhaust arrangement under the car look like this (note the two coolant hoses)?

Profanas · Mar 28, 2022

ChapmanF said: ↑

That hose loop and that second temperature sensor are for the exhaust heat recirculation system, which I do not think is used in all market regions.

I wonder if it is present in Lithuania. Does the exhaust arrangement under the car look like this (note the two coolant hoses)?

Click to expand...

No, my excaust system is very simple, just catalytic converter ant two pcs lambda. Ok thanks for the info, that's mean in the EU we don't have this exhaust system.

Profanas · Mar 28, 2022

edit

Boston2008Gen2 · Mar 29, 2022

ASRDogman said: ↑

I just did the egr system cleaning, and replaced the impeller for the water pump.
I filled up the coolant, s l o w l y, and had not problem. This is the 3rd time I've done it.
Never opened the valve. I've done several different models of coolant changes and never
had a problem. But I always fill slowly, and a little at a time.

Maybe you are filling to quickly?
Click to expand...

How to do EGR system cleaning?

Minh · Mar 15, 2023

Sergey K said: ↑

Sam Spade: The 3rd gens dont have any belts at all. By grill, if you mean the radiator, no its not blocked or clogged and I replaced it. Its brand new and nothing is blocking it.

Mjoo: If it'd be a dirty EGR, wouldn't I see a performance issue and or MPG drop? I'm not seeing that.

TankYoung / Jerry Mildred: the 3rd gen 2011 and up got rid of the bleeder valve. I spent a few hours looking for one. There is not one anywhere. Not on radiator nor the T contraption by the coolant sensor.

Mendel Leisk: Pulling a small hose from the top maybe a good idea. I may try that. Im just worried it will gush coolant everywhere.

I will check the fan speeds and coolant hose temps when it overheats today.

Any other ideas in the meantime? Id love to hear anything.
Click to expand...

@Sergey K. Did you ever find out the issues and have a fix? I am having same issues with my 2011 Prius

Minh · Mar 15, 2023

Sergey K said: ↑

I was recently driving down the highway and saw the engine overtemp light come on on my dash. I pulled over and looked under the hood and the coolant was boiling in the reservoir. Bad sign. Coolant was slightly below the low line from evaporating and boiling coolant coming out of the reservoir cap.

I have a 2011 Toyota Prius Level 5 with 77,000 miles with no modifications of any kind.

PROBLEM: Engine coolant overheats up to 235F while driving at high speeds (65mph) under heavy load (going slightly uphill on highway at high RPMs). At low speeds under 60mph or when the car is idle, no overheating occurs.

Sketch-1550725530879 by Sergey K posted Apr 1, 2019 at 3:59 PM

REPAIRS TRIED:

1. Replaced coolant reservoir cap: I started with the most inexpensive part to replaced: the reservoir cap. I got a replacement from Toyota dealer. If the cap is not holding the correct pressure in the reservoir, the coolant can boil faster than necessary. I replaced the cap and filled up the reservoir to the max line. Replacing this made no effect, I had the same overheating problem.

2. Replaced thermostat: Got a new thermostat from Toyota and replaced it. When draining the coolant, it all came out clean, debris free. Checked the old thermostat in boiling water and old one still worked as well. Installed the new thermostat regardless. Replacing this made no effect, I had the same overheating problem.

3. "Bled" the cooling system: Spent about a couple hours running the car up to temp and squeezing all of the coolant hoses. Had the heater on high with lowest fan speed. Doing this made no effect, I had the same overheating problem.

4. Checked the coolant temp sensor: Removed the coolant temp sensor and tested with an ohm meter according to the Prius service manual. Sensor is working as normal. No issues found.

Screenshot_20190319-134352 by Sergey K posted Apr 1, 2019 at 3:59 PM

5. Replaced the radiator: Some friends kept telling me the radiator is probably partially clogged and is likely the issue. Ordered a new radiator and installed it. Again, old coolant came out clean, debris free. Filled new coolant into new radiator and bled the system again. Replacing this made no effect, I had the same overheating problem.

Screenshot_20190321-204436 by Sergey K posted Apr 1, 2019 at 3:59 PM

6. Replaced the water pump: I left the costliest part for last. But my Prius started showing me 1 engine code: P148F: Engine coolant pump over revolution. I'm not sure if this code was here the whole time or not and I'm not sure what it really means. I bought a brand new water pump and installed it, filled system with new coolant, and bled the system. The engine code went away and I'm not seeing it at this time. Replacing the water pump made no effect, I still have the same overheating problem under heavy load at high speeds.

Screenshot_20190322-205152 by Sergey K posted Apr 1, 2019 at 3:59 PM

I checked the service manual and the 3rd gen Prius normal operating temp is 176 to 212F. Mine spikes up to 235F (and would prob go higher if I didn't pull over right away).

Sketch-1553314740704 by Sergey K posted Apr 1, 2019 at 3:59 PM

Some more notes:
1. I dont think it's a blown head gasket because the coolant does not leave the system except when it boiled over. It stays put at the max line now that I pull over before it boils and the oil is clean and not getting mixed with coolant.
2. Both radiator cooling fans work and blow the correct way.
3. The cabin heater works fine and blows very hot air within several minutes.
4. I'm also using the Toyota brand pre-diluted 50/50 pink coolant. Never used anything besides Toyota coolant.
5. No other engine codes or issues come up.
6. When the car is heated up (over 165 or more), the coolant is going around as the left thick coolant hose stays cool and the right thick coolant hose gets fairly warm.

HELP! I've spent so much money and time and literally replaced and/or tested everything I can!!! I need this car for work. I don't know what else to test. It only overheats under load at freeway speeds. If I drive 60mph or less on flat roads, I see no overheating issues and the coolant always stays under 200F.

Am I missing something? Could I still have an air bubble somewhere in my hoses? What can I do???
Click to expand...

Did you fix the issue or find out what was wrong? I am having same issues. TIA

Shahzad Nayyar · Mar 18, 2023

Check post #35

Minh said: ↑

@Sergey K. Did you ever find out the issues and have a fix? I am having same issues with my 2011 Prius
Click to expand...

Posted via the PriusChat mobile app.

ChapmanF · Mar 18, 2023

Post #35 may have some red herrings in it. Replacing the faulty water pump was certainly important in solving that problem.

There are some rituals being circulated that make filling and burping the cooling system a lot more complicated than what the repair manual says to do, and what's in the repair manual has reliably worked for me.

Need help! Gas engine overheating. Cannot resolve.

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Need help! Gas engine overheating. Cannot resolve.

ChapmanF Senior Member

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