What are the symptoms of a faulty engine cooling fan?

A failing cooling fan often shows up as the engine overheating in slow traffic or when stationary, while temperatures stay normal at higher speeds when airflow over the radiator is natural. You may also hear the fan running constantly, not at all, or making noise as the bearing wears.

What does the engine cooling fan do?

The cooling fan draws air through the radiator to remove heat from the coolant, which is most important at low speed or when stopped when there is little natural airflow. It is controlled by a temperature sensor or the engine management system and switches on when the coolant gets hot.

Will my car overheat if the cooling fan stops working?

It can, especially in traffic or at low speeds where the radiator relies on the fan rather than airflow from movement. Overheating risks serious engine damage, so a non-working fan should be diagnosed and replaced promptly.

How much does an engine cooling fan cost?

The price of an engine cooling fan depends on your exact vehicle and the brand you choose. Enter your registration above to see parts confirmed to fit, then compare prices from the brands we stock on this page. Free UK delivery on orders over £50.

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The engine cooling fan draws air through the radiator when the vehicle is stationary or moving slowly, supplementing the natural airflow that occurs at road speed. A failed cooling fan causes the engine to overheat at idle or in traffic — a situation that can damage the head gasket and cause very expensive repairs within minutes.

Electric vs mechanical cooling fans

Most modern vehicles use electric cooling fans controlled by a temperature switch or the engine ECU. Electric fans run only when needed and can vary speed on multi-speed systems. On older vehicles and many commercial vehicles a mechanical fan is driven directly by the engine via a viscous coupling — the coupling allows the fan to freewheel at high engine speed when airflow is sufficient, reducing drag on the engine.

Viscous coupling failures are common: a worn coupling allows the fan to freewheel permanently rather than engaging when the engine is hot, causing overheating in traffic. The symptom is an engine that runs fine on the motorway (natural airflow sufficient) but overheats quickly at idle.

Diagnosing cooling fan problems

An electric fan that does not run when the engine is hot (with the A/C off) indicates a failed fan motor, relay, temperature switch, or wiring fault. Turn on the air conditioning — the fan should run whenever the A/C compressor is active, regardless of engine temperature. If it runs with A/C but not when hot, the thermoswitch or its circuit is the most likely fault. If it does not run with A/C either, the fan motor or relay is suspect.

A mechanical fan should create strong airflow when the engine is hot at idle. A fan that spins freely by hand when the engine is hot (with the engine off and cooled) has a failed viscous coupling.

Electric fan not running at idle when engine is hot
Engine overheating only in traffic, fine at speed
Fan spins freely by hand when hot (viscous coupling failure)
Fan runs with A/C but not on temperature (thermoswitch fault)
Noisy fan motor or blade catching on shroud

Replacement

Electric cooling fans are typically supplied as a complete fan and motor assembly or as a fan/motor with shroud. Match the number of blades, motor wattage, and connector type to the original. Use the registration lookup to confirm the correct cooling fan assembly for your vehicle.