I have a 99 chevy silverado 1500 5.3L V8 with running hot problems, would be overheating if not for turning on the heat to bring the temp down. I have tried many solutions including the following; 1. Flushed radiator twice 2. Replaced thermostat twice 3. Replaced fan clutch 4. Replaced temperature sensor 5. Replaced water pump 6. Replaced radiator cap 7. Replaced front two O2 sensors 8. Checked all lines Now after alot of time and money and 3 different mechanics there isn't much left that anyone can think of. The mechanics are suggesting it could possibly be a crack head, but they are not confident b/c the truck runs perfectly fine as i can tell with the exception of the temperature. Usually within 10-15min the temp starts rising, but not consistent...other than it always gets hot. Been going on for over a year now... Engine not losing oil, or water... Still has good power... Still runs good... We did check the engine with a laser thermometer, and the engine was hot. Is there anything I can try...Please help and thank you in advance.