Mechanics

Fan Clutch

Step by step guide on how an automotive fan clutch works. This article pertains to all vehicles equipped with a clutch fan.

Step 1 - A fan clutch function is to engage the fan blade to the shaft when heated which is mounted to the front of the engine attached to the water pump. This clutch is constructed using silicone grease, and a temperature sensitive coil spring that expands and contracts with heat from the radiator.


Clutch Fan

Step 2 - The fan clutch is driven from a serpentine belt which is connected to the main drive pulley of the engine.


Serpentine Belt

Step 3 - To remove the fan clutch a large wrench is needed, it might also require a hammer "shock" to unlock the clutch threads. These threads can be standard or reverse rotation.


Fan Clutch Removal

Helpful Information

A clutch fan can fail one of two ways, it can either be locking the fan to the clutch causing poor mileage and a whirring sound, (like an airplane is taking off.) Or the silicone grease can leak out causing the fan clutch not to lock up, allowing the fan to "freewheel", failing to pull air through the radiator, this failure usually is followed by the engine overheating. The clutch fan is utilized at slower speeds while air movement is diminished.

Basic Checks

(Engine "OFF".) Inspect the fan clutch for leakage from the front or rear of the unit, input shaft and temperature controlled expansion spring. If leakage is observed, the fan clutch has failed. Next, grasp the fan blade and turn it, the fan blade should free wheel with some resistance. If the blade spins with no resistance, or doesn't spin at all, the clutch has failed.

History

A clutch fan was developed in the late 1960's and was in full production by the early 1970's. Prior to the clutch fan, an engine was subject to a fixed style of fan that was directly bolted onto the engine. This direct style of fan is not only inefficient, it produced excess noise that was undesirable.

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AUTHOR


Written by
Co-Founder and CEO of 2CarPros.com
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2013-11-22)