Clutch fan options on my 340?

Per hayden.

• 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.


Huh so if it engages at 200 degrees coolant temperature and i run 180-190 would it theoretically never engage? Or since its spining slower would allow for coolant temp to go above 190 in the same setup?
Right now on a spring day with the fixed fan it stays at 180, with the clutch fan would i see it fluctuate more? Could i see it reach 200 degrees before the fan is even fully engaged to cool it back down?