Automotive Cooling Fans
Cooling fans can be driven the crankshaft or by an electric motor. Radiator cooling fans provide air flow through the radiator fins, transferring heat from the engine’s coolant to the outside ambient air. Some vehicles have a fan installed in front of the condenser to assist in heat exchange. The radiator and condenser require air flow to exchange heat to the atmosphere. Are flow created by this fan is vital, especially while idling or when the vehicle’s engine is running while the vehicle is sitting still. When a vehicle sits at a red light, it’s not creating ram air.
When the fan is mounted to the water pump flange, bent or missing blades will cause an imbalance, resulting in damage to the water pump’s bearings and seals. Always check for cracks and excessive wear in today's plastic fan blades.
Viscous Fans: These fans are driven by the crankshaft; it's important to check the belt for wear and glazing. The typical viscous fan clutch contains silicon oil that can leak from the unit. This thick fluids viscosity is measured in CST or centistokes and will wear over time. Check the unit for leaks through the seams and around the shaft. They also have a thermostatic spring that must be inspected. Check it by releasing it from its seat and measuring the distance between the spring and its retainer. Always check manufacturer’s specifications for special procedures.
Electric Fans: Electric fan blades are typically made of plastic and should be inspected for cracks and wear. They’re operated by the PCM and an ECT or engine coolant temperature sensor that senses the temperature of the engine’s coolant. A variable voltage signal is sent to the PCM. The PCM then compares this signal to its internal memory; if the coolant is hot enough, the PCM sends a low current voltage signal to the fan relay. The relay contacts close and complete the fan motor’s circuit, activating the fan motor.