Try useing your temp gun on the front of the radiator unless you have ac then you need to do this on the back of radiator car needs to be at operating temp Your looking for hot and cold spots in the core so your going to have to move it around top to bottom side to side big temperature changes mean the radiator has some issues Blockages not flowing right thru the core You can also use temp gun to check upper and lower hose temp Lower hose should be cooler than top
