My 2003 Honda Pilot started overheating and the temperature on my dash is fluctuating. I don't know what it is. The coolant is full no leaks, the lower hose is colder than the upper hose, the water pump was replaced about 5000 miles ago and the fans are running properly. I'm not sure whats wrong with it. I opened the radiator cap and there was some white steam/smoke coming out when the engine was hot. is that Normal? How do I fix this? the car has been sitting for a month too if that helps.