I need a little advice. I have a Cat 8C20. I run it to get it warm and check the radiator with an infra-red thermometer. The top tank outside temp registers at about 135-140 degrees and the lower tank outside temp registers at about 120-125 degrees. When I turn it off it will burp a little bit of coolant out of the overflow tube.
Is this normal? I thought perhaps the thermostat is sticking. Any thoughts? Thanks in advance!

I'd be more inclined to think you have an air pocket in there somewhere that is slightly compressed or trapped when water is circulating and burps when not.

Hi CWC,
possible combustion leak, head gasket, re torque cyl. head, check for restriction in lower rad. hose causing pump to pull air in through water pump seal/ packing, rust flakes, sediment ,collapsed inner wall of hose but outside looks ok. Saw a hose on a mates ute which had seperated inner wall which had air trapped in between the layers, when checked off vehicle cold looked ok, sat it in the sun and watched the bubble grow!
Temp differential looks ok, but at lower loads may be ok and o/heats when worked. This is a start check list.
Hope this helps
Eddie B.