Clutch fan question

So I've been having a debate with a friend at work.

Clutch fan is suppose to "lock up" when the motor reaches operating temperature(not really "lock up", but present more resistance when turning the fan blade, compared to when the motor is cold.).

You should be able to check if your fan clutch is operating correctly by, turn the fan blades when the motor is cold, and rechecking after driving the truck to operating temp, noticing more resistance in turning the blades with a hot motor, correct?

 

Yes that is correct. Keep in mind I was still able to stop my fan with rolled up paper at operating temperature.

 

Isn't being able to stop the fan with a rolled up news paper a sign of a failing clutch fan?

 

This is what I've heard.

 

This is one of those trick questions .

It is not so much engine temperature as under the hood temperature .

In the cooler weather here in Winter my engine is at operating temperature being controlled by the thermostat yet my fan clutch never gets hot enough to engage .

Summer time pulling a grade loaded @ 1000 pounds pulling another 2000 pounds then the fan clutch is engaged

Yet my Temperature gauge still reads the same in those 2 examples

It is quite possible the newer ones work different I can only go by what I use.

 

This concept is correct, but in reality it doesn't work like that. There is a fluid inside the clutch that gets more viscous the hotter it gets. There is also a bimetallic strip on the outside of the clutch that changes tension with temperature. At normal operating temperature (ECT reading 180-195 or so) you will still be able to stop the fan. It will be harder to stop than when it is cold, but you will still be able to stop it.

Now if your engine temperature gets up above 200, it may actually lock up and you would not be able to stop it. I have not had my engine that hot to be able to test it.

I did this test with my old clutch (175k miles) and a new Aisin replacement, and both performed exactly the same.