Q: My car sometimes overheats when in traffic. I also hear a loud fan or belt noise. What’s going on?
A: When moving down the highway air is forced through your car’s radiator to help cool the engine. Your radiator fan is also designed to draw air through the radiator to assist in this cooling process, especially at slow speeds or when stopped. Depending on your vehicle, you either have an electrical fan or one that is mechanically belt driven. If you are hearing a belt noise, check the belt tension. Do this by pushing down on the belt between two pulleys when the engine is off. You should only have about a half inch of deflection (movement) for each foot of length between two pulleys. If you have more deflection than this, the belt may be loose and slipping. Also inspect the belt to see if it is cracked, glazed, torn, or if pieces are missing. But remember newer belts may look perfectly fine but could be worn out. A slipping belt can also cause the water pump not to circulate the coolant efficiently. If your vehicle has an electric fan, the sensor that sends the signal to run the fan or the electric motor itself may be faulty. Remember to always work on an engine when it is off and that an electric fan can start at any time even when the key is off. Disconnect the negative battery cable for safety.