Hello again,guys! I haven't been on here a whole lot because my '03 4x4 Blazer runs so darn good. Recently, I had to replace the radiator because a crack developed in the structure. My 4.3 V6 runs at just below 210 degrees while it's running. When I stop and turn the key off and it sits for a few minutes, the temperature will read around 230 degrees when I start it back up. It will then cool itself back down to just below 210 while it's running. I've tried burping the air out several times and the heat in the cab blows HOT. I know my coolant is circulating while driving the truck. What causes it to heat up after I shut it off? It's currently full of the proper coolant in the system and in the overflow tank as well. Thanks in advance for any help.

 

Pretty much normal operation. When the engine is running, coolant is flowing through the block absorbing heat from the combustion process. It flows through the rad, shedding the heat into the air flowing through it. You shut off the engine, the flow stops. The heat retained in the engine metal still transfers to the now stationary water, heating it up but it has no way of quickly shedding that heat so the water temp rises. Once you re-start, the water flows again, the heat is shed, and the temp drops.