2005 Prius coolant reaches 230-240F when driving on highway

Is the Torque instrument calibrated correctly?
Have you used other measuring instruments for comparison?
A faulty measuring instrument can show the temperature on the surface of Mars and inside a volcano vent at the same time.

 

Yeah what are you using to measure this temperature where are you getting this reading from TIS Toyota software freeze frame data etc? You actually should be able to smell this kind of temperature when you open the hood You don't generally forget it I got four generation twos here I couldn't make that kind of boiling coffee water if I wanted to and I'm in the 100° weather in the southeast United States for five six months of year. I'd have to put a piece of cardboard in front of the radiator for 40 minutes possibly more. And what else is happening at this 2:40 if you whip over on the side of the road or pull back into your driveway and whip the hood up what's happening The two main hoses to your radiator for the engine should be so tight you can't even touch the hose because of the heat and it is harder than a 700C bicycle wheel pumped up for a road race holy Jesus so there must be something seriously wrong if you've done all this other work. If you back the fans on the back of the radiator away from the radiator with this kind of heat going on and you run your hand across the core of the radiator relatively quickly is there a big cool spot in the middle? This is a thing. If so your radiator core is plugged and your radiator fluid is going around that plug the cold spot and the hot areas around the radiator or where the water's trying to get past the plugged area very common You need to find out about this quickly before you burn up your engine I would say you've got a hold up probably from stop leak in the bottom core of the radiator assembly that handles the ice engine this has nothing to do with your inverter or any of that My guess would be the radiator core is plugged jump that out or change that core and probably the problems gone In a shop you could take a water hose and make a fitting and connect it to the radiator hose and a container and see what happens but if you feel the cold spot in the middle of your core in the midst of this then you know where your problem was My buddy at the radiator shop diagnoses this hundreds of times a year in the southeast United States on all kinds of vehicles that need coolant to not overheat.

 

Has anyone ever put any additive into your cooling system (ie. stop leak, gasket sealer)?