Prius intermittent temp light when driving uphill

i'm no expert, but i would be worried. idk what temp sets the light, but it can't be a good thing

 

Did you install a Toyota OEM water pump or an aftermarket pump?

 

Certainly not normal with the noise and coolant running too hot.

 

Usually, the trapped air will bleed itself. In my old 1985 Corolla LE FWD, if air was trapped during coolant drain and refill, there would be no coolant circulation whatsoever. The solution was as easy as pumping the coolant by repeatedly squeezing and releasing the upper hose and then adding more coolant. Also, the jiggle valve on the thermostat, which helps bleed the coolant, needs to face up.

You use a 50/50 water/antifreeze mixture, right? Using a higher antifreeze concentration will result in a lower cooling efficiency and higher coolant temperatures.

Check for leaks and a bad radiator cap. If no leaks are found, it could be an improperly installed head gasket that is sucking air or perhaps a a bad or improperly installed water pump.

 

Comparing 1985 gasser car to a 2011 hybrid car for troubleshooting contrast, mice

 

You made it onto the archive.

 

206f on a steep hill in hot weather is ok. But you said 206+. Does that mean 240f or higher? Typically the light comes on at 248f.

Gen3 has two engine-coolant temperature sensors to monitor and either one can flash the light. One is on the engine while the other is on the hose coming from the exhaust heat recirc system. With Techstream one is in the ecm pids while the other is in the Combination Meter group. Both are called Coolant Temps.

As noted in a July 14th post, the exhaust recirc thermostat could be stuck in the heat exchanger position adding unnecessary heat after warmup. This was reported at least twice now. The engine temp could be fine but the exhaust heat exchanger sensor (Combination Meter ecu) could trigger the light.

I use the Car Scanner app to display both engine-coolant temps.



Normal capture of both temps (Exhaust Heat Coolant Temp in Red)


Overheat light caused by a stuck exhaust heat recirc valve. (Exhaust Heat Coolant Temp in Red)


In the above Car Scanner capture the red trend exceeds the other sensor but not enough to trip the warning light in this test run. However the owner MSB87 replaced parts of the exhaust heat recirc system and eliminated the problem.

 

Did not compare. That was only a mention in a lengthy post. He likely has an air leak, which could be from the head gasket or water pump as I explained.

 

But the coolant is bubbling, which means there is an air leak unless there is an unlikely air-bleed issue.