2004 Frontier, How to test fan clutch?

[Q451990]

The service manual doesn't say much about the fan clutch other than to check for wobble, leakage, or bent fins. There are a ton of YouTube videos about this, but as with all things YouTube, opinions vary. Some make a big deal about how long it takes for the fan to stop spinning after turning the car off. Some talk about the "rolled up magazine test."

So how do you guys test a fan clutch? In my truck, it seems like it's always doing the same thing. Right after startup, you can't stop the fan with a rolled up magazine. Same after it's been running for a while. Feels the same cold, or after a long drive with the truck off. The fan never roars after the truck heats up like the one on my Q45 does.

As best I can tell the cooling system is fine. I spent some time with an OBDII scanner hooked up to it today, and the temperature stayed under 180F on a 10 or 15 minute drive in the hot sun on a 90 degree day. I let it idle for 10 minutes, and it still hovered just a little over 180F. I think 185F was as high as I saw.

I have a slight bit of play in the clutch side to side, maybe a mm or two.

Any thoughts?

[VStar650CL]

The main job of the clutch is to offer more resistance as the airflow off the radiator gets hotter. The little clockspring on the front of most types is a bimetal that uncoils as it heats up. That works a valve which changes the flow through the viscous coupling inside. The upshot is, spin the fan cold, it should spin with little effort. Then take a Bic lighter or torch to the bimetal and spin it again. It should take much more force to spin the fan with the bimetal hot. If it still spins freely, either the fluid has leaked out or the valve is bad.

[Q451990]

Interesting. I'll have to try that and see what happens.

[Q451990]

So I tried the lighter test. With it installed on the truck, it's a little difficult to get to. From what I could tell, nothing changed after heating it up. How long would you say you have to heat the spring with the flame to notice a difference?

Also, how common is it for fan clutches to fail?

[VStar650CL]

It should have responded even to a little heating, it's designed to work at radiator outflow temperatures (say, 130~180F). So your fluid is probably leaked out. They all die sooner or later from old age, either they leak or the bearings go bad.

[Q451990]

I'm beginning to wonder if the one on my Q45 is bad too. They both act about the same. I can spin the blade about 3-4 blades with my hand regardless of temperature. Our 4Runner has a clutch fan, so maybe I'll play with it to see how it behaves. I just hate to spend money without really knowing that I have a problem.