If the temperatures vary by 30-50 degrees and the thermostat is working, chances are it's restricted. With IR or without this you can also check it with the palm of your hand. First after the engine is warmed up shut it off and feel the upper and lower radiator hoses to see if the temperatures vary. If restricted chances are the upper hose will be very hot to the touch while the lower will be just warm. Once again that is if the thermostat is functioning properly. Also if you have access to different parts of the radiator core itself (the finned middle portion) feel it with your hand in different locations to feel for temperature variations. If temperatures vary, (you already tried flush or reverse flush the cooling system,) but your best bet is to have it boiled out by a Radiator repair shop, because at this point flushing is usually only a temporary fix. My thinking is the flushing may have caused some blockage.
The older I get.. the faster I was....
Last edited by Tom Frasca; 06-09-2019 at 04:46 AM.