Checking calibration of engine temp gauge with candy thermometer....

[Dans 68]

Reading previous posts on measuring the temperature of the radiator fluid with a thermometer as a sanity check on the dash temperature gauge spurred me to do the experiment today. I even used an infrared temperature measuring device on the water pump exterior to obtain another sanity checkpoint. One unexpected discovery was that my thermostat opened at just under 160 degrees; I had always thought it was a 180 degree unit.    Live and learn (and test!)

So, I started the car with the radiator cap off, candy thermometer probe fully immersed in the coolant. As mentioned above the thermostat cracked open around 160 degrees and slowly climbed up to a maximum indicated, corrected temperature of about 185 degrees (as shown on the candy thermometer) after 15 minutes of idling. I did calibrate the candy thermometer by inserting it in a pot of boiling water ans seeing how far from 212 degrees it was. It read low by about 5 degrees.

The 3 attached photos tell the story. At a corrected (candy thermometer) temperature of 185 degrees Fahrenheit, with the infrared thermometer in close agreement with the candy thermometer temperature, the dash temperature gauge read 197 degrees Fahrenheit (I extrapolated the value  ). So, I'm reading about 12 degrees hot on the dash temperature gauge. Good to know when that gauge starts climbing.  

Dan