i've fought bad temperature gauges and sending unit reading higher and lower than the actual internal temps were. I now check all suspicious cooling problems with two different heat temp guns to mak esure what the gauges are reading are accurate.
I had one of Autometer expensive race mechanical 320 degree reading on the face temp gauges reading 140 F when I could put my hand on the thermostat housing it wasn't hot at all, sticking my finger in the radiator with the electric water pump circulating the water found it below body temperature
Trust but verify