Coolant level?

You have enough coolant. If adding a little buy a gallon of distilled water. However I would be more concerned about the engine or inverter water pump. Usually you can see flow from the bottom hose of the engine reservoir after it completely warms up. A flashlight through the plastic helps see it. The inverter reservoir will kind of bubble or agitate as seen with the cap off.

There are several temperature codes and sources. Running without ac might help a marginally functional system but only if the light stays off.

Honestly I would find the nearest Toyota dealer and stay near there until Monday. Be there when they open. Otherwise you need a bluetooth or hardwired obd2 scanner capable of reading coolant temp in realtime along with codes. Some autosupplies sell them for maybe $100. Then use Car Scanner or Torque or similar phone apps.

Driving an overheated (over 205f) engine can and will kill the engine. I believe the light comes on around 221f. If you are close enough to home, consider having it towed or trailered home.

 

What’s the miles on it?

The level is not bad; if you’re going to get coolant I’d stick to Toyota Super Long Life, readily available at aforementioned Toyota dealership, say Monday if everyone’s closed today.

 

Your cooling system is probably partially clogged or your water pump isn't working properly. It was a hot day in the valley, yesterday 105 F+, with the AC and pushing the car at over 75 mph - the cooling system needs to be at peak performance.
How many miles on her and has anyone mixed anything into the coolant? If Toyota coolant isn't available, the best course of action is to top-off with distilled water. While some non-Toyota coolants claim to be compatible - I wouldn't take a chance of mixing it in. I've seen chemical reactions that has turned coolant into brown sludge - destroying both the cooling system and engine.

Hope this helps....

 

In the repair manual procedure for filling an empty system:

Toyota Service Information and Where To Find It | PriusChat

you first fill all the way to the B line on the bottle, and then you put the cap on and run the engine up to temperature and several more minutes for all the air in the rest of the system to burp out. The air just trades places with the extra coolant in the bottle, and when everything is cooled down to ambient temps again, you see that the engineers knew how much air that is, and the level has dropped from B down to FULL.

205 ℉ is roughly 96 ℃, barely above the 95 ℃ where the cooling fans turn on. I would not be concerned to see 96 ℃ on my ScanGauge when the car is doing honest work.

221 ℉ is 105 ℃, which is a special temperature for the car (more below), but is not, as far as I know, where the overheat light turns on.

There are two coolant temperature sensors, one in the cylinder head, and one in the hose coming back from the exhaust heat recovery system.

I have tested what reading from the EHRS sensor will turn on the overheat light, and that was 120 ℃ (or 248 ℉).



I have been kind of assuming it would be the same temperature from the cylinder head sensor to light the red light also, but I have never tested that. Might be worth doing, just to complete our understanding of that.

So what's special about that lower, 105 ℃ temperature? Well, that's special if there is a known water pump problem (and the check engine light is already on because the ECM knows about the pump problem). In that situation, if the ECM sees the temperature hit 105 ℃, it stops the engine on the spot, no extra warnings or discussion, not even an overheat light because that only comes on at a higher temp. You're just suddenly driving without an engine, and the red triangle comes on (P0A0F, the power management control ECU saying "I don't know what happened, but the engine won't run"). So that's a surprise you can get if you ever have a check-engine light for the water pump and try to keep driving. But I don't think 105 ℃ is normally considered overheated as long as the pump is working. (That is, it's definitely pretty warm, well above where the fans turn on, but below where you'd see the red light.)

 

He was probably on the road this morning before the moderator allowed his post from 7:13 pm yesterday.

According to some a temperature warning light is not as important as a long rambling non-answer.

 

I didn't see that anyone else had answered the first question in the first post yet.

"Thank you for catching that" is another possible thing to say when someone has corrected details that were off in a post. There are a lot of posts where I've said that when somebody did that for me.

 

I told him his level was fine. Driving with a temperature warning light is dangerous. If he had a temp monitor it should stay below 205f.

 

Agree that driving with the temp warning light is dangerous. The light only comes on at much higher temps, so when the light was on, the coolant was much hotter. 205 ℉ is still roughly 96 ℃, barely above the 95 ℃ where the cooling fans turn on, and is not by itself a threshold of overheating.

 

A very unreliable vehicle........especially after 150,000 miles