Thanks for the replies so far. I do have an infrared thermometer. I added a little more 50/50 coolant in there today. By the time I got home the temperature was still up to about 110 degrees celcius but would not go any higher. I parked, turned off the engine and opened the hood and saw that the coolant was BOILING in the reservoir. I'm letting everything cool down, and I will see if the auxiliary fan is running.

Should I use the IT to measure the coolant temp?