If you are using a infrared thermometer (pyrometer) be aware they often misread on shiny or semi shiny surfaces, a piece of black electrical tape on the shiny surface and the reading will be good, as mentioned before a cheap digital meat thermometer from the hardware or bbq store is great to put into the radiator, and also to confirm the infrared readings, btw infrareds do work well pointed at water, at least it does when it’s coming out of a faucet.
