Very Loud Fan
 

I know there a lot of posts about a loud fan with the cause being a seized fan clutch
BUT
the diagnosis usually involves trying to turn the fan by hand and finding it very difficult, thus indicating a seized fan clutch.
My problem is that even though my fan stays on all the way to redline, as well as being insanely loud and going as fast as possible all the time, I am able to easily move the fan blades with my fingers w car off. No resistance, although it is not quite free spinning, i can move it without difficulty with just one finger.
If a new fan clutch would fix it, i would do that as i think it would be easier than an electric fan.
But it seems that my fan clutch isn't seized since i can spin it.
I do not want to buy a fan clutch to find that did not fix the issue.
Furthermore, if i were to get an electric fan, would i need to upgrade the alternator?

Even with a faulty fan clutch you can still spin the fan by hand. You will just feel more resistance than you would if the fan clutch were working properly. I would replace the fan clutch if it were suspect.

You can spin it freely when hot or cold?
 

There's a bimetal strip in the front of the fan clutch heatsink that bends when hot, as its a sandwich of two dissimilar metals that expand at different rates. When this strip gets hot, it bends and opens an internal orifice that controls silicone fluid flow within the fan clutch. When cold, it should spin freely by hand. When hot, the silicone fluid will add resistance on the internal vanes of the assembly and make it difficult to turn. This is what makes the Factory fan clutch solution so elegant - it is temperature controlled and follows a continuous modification cycle which is easier on engine and radiator temps vs. a discrete (*on or off) fan solution like electric fans do. Also, at speed, when the air flow serves greater cooling power through the radiator, the fan clutch free wheels, reducing overall mechanical drag on the engine.

The hot air coming through he radiator is what signals the bimetal strip, so if it's seized, that's an internal failure within the fan clutch. They can be rebuilt and refilled with heavier weight silicone fluid, which is common in hot environments and with more accessories creating more engine heat to be dealt with, along with the expected noise increase of the fan clutch operating for more of the Engine rpm range.

Replace the fan clutch,it is defective,you're not wasting your money.

Thanks, LongDuck, I always wondered how the unpowered clutch works, and maybe mine had failed, as it doesn't spin freely, and is loud even when the car is started cold.

Well poo,

I did some digging around and cannot find one for my 79. The 79-80 shared the same one, but the 81-83, and the 84-85 are different models. They are also over $250 bucks on Mazdatrix.

I also found this youtube video about the clutch, and how the fluid gets back to the reservoir.

Normal for cooling fan to be engaged on cold startup for about 20 seconds at which point it will declutch.

That's odd, mine does the exact opposite, it's free wheeling on start up, then spins with the motor. The only time it doesn't is if it's below freezing, then it's silent till it warms up a bit.

Mine like this. It will sound like a jet taking off for 15-20 seconds and then it's quite (normal).

Mine has never free wheeled.

I have it off the car right now so I've cleaned the crud off the front and under the metal strip that is on the front of it. Sprayed some wd40 on it, and after a few hand twists it started spinning free. After i set it down for awhile, it gets stiff again. So, maybe cleaning it up may have freed up the mechanism. Will hopefully find out before the end of the month, the engine is back in the car, and all the all the bits, but the exhaust, are back on it.

I have a stash of about four good clutch fans and one bad one. The bad one will "Free-wheel" while the good ones will only make it one or two spins and have a fair amount of resistance.

Thanks for that video Todd, that makes a lot of sense about something that's always been a mystery to me.

Good luck getting yours working again and if you can't you should look around for a used one, should be plenty with folks shifting to efans (clutch fans are better).