I have a 1996 C/K 1500 Silverado with 122k on it. When I start up in the morning the temperature rises steadily past 210 to about 250 with the "Check Gages" light coming on. Once it reaches this point, it will usually back off like the thermostat finally opened. When I drive the truck later in the day (heading home from work), I don't seem to have any problems. Several thermostats have been tried and the water pump was replaced recently. Does anyone have a clue of what is causing this problem or how to further diagnose?
TIA