I have a 2003 Honda Civic with an overheating problem. It does not leak any coolant or even steam up but the temperature gauge goes up and it smells hot. I have had the thermostat, radiator, fan sensor, fan, water pump and timing belt replaced with no results. It runs fine for a few days, but always starts overheating again. I have left it at my mechanic for several days and he lets it run and it doesn't overheat but as soon as I get in it and start driving around, it goes right back up. What else can I do?