[VetteVet]

Fan Clutches & Fan Blades

Fan Clutches


Fan Clutch Operation & Troubleshooting
The Fan Clutch is a component of the cooling system that varies the fan speed to meet the cooling needs of the engine. Nearly all rear wheel drive vehicles use Fan Clutches to control fan speed because of their ability to provide high volumes of air and good fuel economy. Despite their popularity, they are one of the least understood cooling components. There are two types of Fan Clutches, the Non-Thermal (also called centrifugal clutches) and the Thermal Fan Clutch.


Non-Thermal Fan Clutch

Low cost alternative for some standard thermal clutches.
Always engaged, less fuel savings than a thermal clutch.
Spins at about 30-60% of the water pump speed.
Shorter life expectancy.
Cannot replace a heavy-duty clutch.
Identified by the smooth, steel faceplate, (without a thermal spring assembly), on the front.



Thermal Fan Clutch

Varies the fan speed with temperature of the air behind the radiator.
Engaged (high speed) operation provides maximum cooling.
Disengaged (low speed) operation provides fuel savings and noise reduction.
Greater life expectancy than a non-thermal clutch.
Briefly engaged at cold start-up.
Engages at about 170° radiator air temperature, (about 30° lower than coolant temperature).


The air temperature coming through the radiator is sensed by the bi-metal thermal spring on the front of the thermal fan clutch. It expands and contracts with the change in air temperature operating a valve inside of the clutch. When cold, the silicone drive fluid is pumped from the working area to the reservoir. When hot, the valve opens allowing fluid from the reservoir to be transferred to the working area thereby increasing the fan speed. The clutch disengages as the air temperature decreases, closing the valve and allowing the silicone fluid to be pumped back into the reservoir.

A thermal fan clutch is engaged on a cold startup because the fluid drains into the working area when the engine is shut off. The fan clutch will slow down shortly after startup as a result of a pumping action produced by a difference in speed between the shaft and the body of the clutch.

Most models are designed to duplicate original equipment performance. Some Chevrolet/GMC truck models are specifically designed to engage at lower temperatures than the original equipment parts that they replace.

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What this means is that the fluid controls the speed of the fan based on the air temperature of the air between the radiator and the fan. The more fluid the faster the fan turns, depending on the air temperature. Since you have lost fluid the fan may not spin as fast as it needs to in order to draw enough air through the radiator to cool the engine coolant. There is a seal on the shaft of the thermal fan to contain the fluid and it shouldn't have leaked any fluid. It may not leak in the vertical position and it may not have lost enough to affect the cooling, or it may not spin fast enough to keep the engine cool.

I would not take the chance especially for any distance but for short drives you could test it and see how it worked.