The small but important part of your cooling system

Ever heard of a fan clutch? It’s a small part of your engine’s cooling system that can sometimes fly under the radar. However, it is a vital component in ensuring optimal performance in your car.

Engine cooling fans help remove excess heat generated in a running car, by drawing air from the radiator. The fan clutch is the part of a fan which regulates fan speed when engaged. Depending on the type of fan, this may be contingent on certain engine temperatures, or simply runs constantly.

Without the fan, your engine would overheat and your car would be undriveable. If you’ve noticed reduced cooling performance or some odd behaviour from your car, it may be due to a malfunctioning radiator fan. So, what now?

Getting to know fan operation

First, let’s touch on how the fan works with your cooling system.

Initially, the fan spins loosely until the engine reaches a specific temperature. The clutch is then engaged, forcing the fan to spin faster and therefore accelerating cooling.

A thermal fan clutch uses a thermal spring (bi-metal temperature sensor) placed on the face of the clutch to gauge heat, and based on this is, it engages or disengages. A non-thermal fan clutch is always engaged and is dependent on engine revolutions per minute (RPM).

The fan is usually located between the radiator and water pump in the engine bay and is driven by a belt and pulley. The common arrangement is where the clutch is mounted on the water pump or other belt-driven pulley, which derives power from the engine.

Types of fans

Nowadays, most modern vehicles utilise an electric fan.

It works a little differently in that the fan operates independently rather than by a clutch, and is instead controlled by a switch at the engine thermostat. Electric fans are usually lighter and have a clearer performance benefit, especially in high-powered engines.

Mechanical (or belt-driven fans) typically come in two kinds — thermal and non-thermal.

The key differences are as follows.

Thermal:

• Engages based on ambient temperature
• Senses heat via bi-metal thermal spring
• Less fan noise
• Longer life span
• More efficient use of engine power

Non-thermal:

• Dependent on RPM — runs based on water pump shaft speed
• Provides steady flow of cooling
• Constantly engaged clutch
• Generally lower cost
• Higher fuel usage

Fan bearings’ essential role

You might be thinking we’ve covered all there is to know by now. Well, not quite. We may have gotten to the nitty gritty, but there’s one more component to a fan clutch that you need to know about — the fan bearing.

A fan bearing (or pulley bearing) is the part that the fan spins on, and requires reliable operation to keep it running smoothly. A damaged or malfunctioning bearing can lead to some not so friendly issues.

Signs & symptoms

There are several reasons your fan clutch may malfunctioning, but a common possible cause is the bearing. Some indicators include:

• Leaking fluid, build up around the bearing or spring
• Seized, rough turning or excessive play of the bearing
• Fan doesn’t turn at all
• Loud fan noise at every speed
• Fan speed does not decrease or increase as expected
• Poor air conditioning performance and overall cooling capacity
• In extreme cases, overheating