Q: Car Overheating; Unknown cause

The coolant could be low, the thermostat could be plugged up or sticking, the radiator could be plugged up restricting the coolant flow, the water pump could have failed, or the head gasket could have burned causing the engine to overheat. Check the coolant to see if its full. If the coolant is full, then feel the upper and lower radiator hoses and see if they are about the same temperature. If they are, then the radiator and water pump is working. If they are not, then either the water pump has failed or the radiator is plugged. If the engine overheats when at a stop, then it would be a radiator. If the engine overheats at any speed, then it would be a water pump. Now, if the hoses are the same temperature, then the thermostat may be sticking or plugged up. To test this, turn on the heater and see if it blows hot or cold. If its blows cold, then the thermostat is sticking closed or plugged up completely. If there is no signs of a failed thermostat, then the head gasket has burned. Usually you will get a white smoke or a sweet smell at the exhaust system if the head gasket is burned up. If the engine coolant temperature gauge says that the engine is overheating, but the actual temperature is normal, then the temperature gauge or the sending unit is not working properly. If you need further assistance with your vehicle overheating, then seek out a professional, such as one from Your Mechanic, to help you.