My " 92" Tercel is still overheating. I have had a new radiator put in and changed the thermostat and I know the fan works. I can't find any leaks in the system either. It only overheats when I am idling. What is wrong with my car? I took it to a local mechanic and he said that the head gasket is blown but I do not find water in the oil or oil in the coolant. Please help.