How fast should a fan clutch spin when the engine is cold?

[jalexquijano]

I checked the fan clutch yesterday when my 240z was cold and it is not spinning freely. If you turn it, it only spins 1/3 to 1/4 of the full cycle. If this is the case, should i order a new fan clutch and wáter pump with gaskets also? Who sells original OEM Nissan fan clutch and wáter pump? My car was made in January 1972 and carries a plastic fan blade.

[siteunseen]

When the fan clutch goes bad it spins more, by hand. I put a new one in my'72 and spinning by hand it won't even make a complete rotation cold. They have oil in them and when it's hotter it frees the fan up. I know that sounds backwards or at least to me, but it's not. Before starting it for the day it should only go around once if that much. A more dangerous way to test them is trying to stop it while the motor is running, if you can it needs to be replaced. I've read using a piece of wood like a broom handle against the aluminium hub is how you do it, not me though! Mine was less than $20 at Advanced Auto.

[Zedyone_kenobi]

Check with courtesy nissan

[zKars]

http://www.haydenauto.com/upload/HaydenAuto/Documents/Cat_Imperial/2007-imperial-fan-clutches.pdf

Perhaps this finally will clear up the "is the clutch locked up cold or hot?" confusion of the day.... Read the paragraph on "Thermal Fan Clutch"

[siteunseen]

Silicone fluid, not oil. Today's lesson!

[Captain_Zeros]

When the fan clutch goes bad it spins more, by hand.

They can fail in the opposite direction as well, mine seized solid as if the fan was bolted straight to the pulley. Sounded like a jet plane above 1500 rpm.

[siteunseen]

They can fail in the opposite direction as well, mine seized solid as if the fan was bolted straight to the pulley. Sounded like a jet plane above 1500 rpm.

That's a good point. Sound would be the easiest way to tell. With a new one, on start up it's a lot louder for the first few minutes. The fan noise definitely gets quieter after it warms up.

[TomoHawk]

When I start my engine, it's quiet for about a minute, then gets louder for a couple minutes, the quiet again, then loud...

I assume it's working correctly, because it's new.

It seems like we should get the severe-duty thermal clutch, because it's supposed to spin at a lower RPM (20% of water pump speed.)

Could you use one with a flex fan?

Edited April 2, 2014 by TomoHawk

[Mark Maras]

Having experienced clutch seizure, The noise is a lot like small plane prop. & HP drops about 25%. I drove my Z with a flex fan (no clutch) over 100k miles and had no complaints. Mine has a 2" spacer which sets the fan 1" from the radiator instead of 1 5/8". Fan diam. is 15" & acually gets quieter at higher RPMs. If you watch it as you rev the engine the blades flatten out. The individual blades are quite large 3 1/2" x 5 1/4". At the time I thought I would add a shroud but didn't need it after all. My orig. fan had steel blades & weighed a lot. with the FF, the engine reved noticeably quicker.

TomoHawk, I don't ever remember my fan clutch, for the few years that it lasted, cycling as you described.

Confession, I drove the car daily without a fan in the summer time for 2 weeks. This is what I learned. RPMs are heat. Duh! Keep the revs low and shut it off instead of idling. I found that at 10 MPH or above I could keep the car at the normal temp. this way. I came to realize that it doesn't take much speed at all to make a fan useless. i wasn't entirely sure if the FF would solve my overheating at idle but i was totally satisfied.

Edited April 2, 2014 by Mark Maras