4 Wheel Drive/SUVs: temp gauge reaches 230, chevy silverado, fluid leak

Question
I have a 1999 Chevy Silverado that had developed a fluid leak it was due to a bad thermostate seal. I had the seal replaced and then added my coolant. After the seal was replaced I had my temp gauge constenly telling me I was about to over heat. I changed the sending unit and the thermostate and flushed the radiator. All of this done I am still hitting 230 degrees, yet when I turn on the heater my thermostate goes down to normal operating range. Is ther something that I have failed to do?  

Answer
Anthony,

I have seen this happen due to air in the cooling system.  Sometimes when changing components such as a thermostat, you have to bleed the cooling system.  Another possibility, is that when you flushed out the radiator, you loosened up some contaminants such as rust, and actually plugged the radiator tubes.  This would explain why it cools down when you turn on the heater.

I would try flushing the radiator again.

This is assuming that the water pump, and cooling fan are working properly.

Carl