Fans - clutch vs. fixed? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

msgross · 01-27-2009, 10:25 PM

My truck has a 5 blade clutched fan..

How do I know if the clutch is good/bad?

What about going to a fixed fan (clutchless)?

Thanks...

**clay68c10** · 01-27-2009, 10:51 PM

If the thermal clutch is good, you can hear the fan kick on and off when the eng is hot. You should also feel the difference in airflow.
If you have a non-thermal clutch, then I'm not sure, I've never troubleshot one.
The thermal type will have fins all over it and a coil facing toward the radiator.

big_al_71 · 01-27-2009, 10:56 PM

Off topic, Mike why not just switch to an electric fan? in the hot florida sun all my vehicles I always have switched to electric fans they cool so much better.

chris71 · 01-28-2009, 10:59 AM

mike i have a fixed fan that i got off of a suburban , and i have no cooling issues even with an old rad. if the clutch on the fan is leaking a greasy-like fluid, it needs to be replaced. the purpose of a fan clutch from my understanding is to engage/dis-engage the spinning of the fan when it is needed or not needed. at start-up and highway, the clutch is not engaged and the fan will not spin as much, i supose to free up some of the stress that the motor uses to spin the fan, freeing up more hp i suppose. the thermostatic coil on the outside of the clutch moves the clutch fluid on the inside to make the fan spin or slow down.

okay, i just found this, this should help.

http://en.wikipedia.org/wiki/Fan_clutch

also if that bi-metal coil is broken or missing, you should replace

50MOTORHEAD · 01-28-2009, 11:18 AM

The trouble with most fixed blade fans is that they usually sound like a jet taking off,,,,all the time. My 67 had a 6 blade ,flex fan. MAN,,you talk about loud !!-KB

Sinister · 01-28-2009, 11:21 AM

I've got a nylon flex fan, quiet and keeps my 350 at 190*

chris71 · 01-28-2009, 11:40 AM

be careful if you are shopping for used original fans, i have heard many stories of fan blades going through hoods because the rivets were compromised in some way. i.e. some rivets were missing, cracked blades, etc.

msgross · 01-28-2009, 04:52 PM

I have heard that about the flew fans... My original fan is a little rusty but seems to spin ok... It does have a slight amount of oil on the shaft but nothing bad for a 40 year old fan...

My hesitation in going with the fixed fan is a slight loss of power and the constant noise. If I see that my clutch fan isn't cooling enough then i'll just replace the clutch...

thanks for the tips guys...

01-27-2009, 10:25 PM	#1
msgross Registered User Join Date: Jul 2006 Location: Central PA Posts: 12,201	Fans - clutch vs. fixed? My truck has a 5 blade clutched fan.. How do I know if the clutch is good/bad? What about going to a fixed fan (clutchless)? Thanks... __________________ The Garage: 1968 K-10 SWB - "Project Money Pit" 1996 Z-71 - "huntin rig" 1969 C-10 LWB (SOLD) "Project flip that truck or else" 1993 Passport, F@rd 1-ton (SOLD)"Project Cousin Eddie" My Garage Build "The 1,000 footer"

01-27-2009, 10:51 PM	#2
clay68c10 Senior Member Join Date: Aug 2004 Location: Centennial, CO Posts: 2,990	Re: Fans - clutch vs. fixed? If the thermal clutch is good, you can hear the fan kick on and off when the eng is hot. You should also feel the difference in airflow. If you have a non-thermal clutch, then I'm not sure, I've never troubleshot one. The thermal type will have fins all over it and a coil facing toward the radiator. __________________ ClusterTruck: 68 C10 Bought in 89, wrecked in 03. Slow low $ rebuild started '17. 6.0 & TKO http://67-72chevytrucks.com/vboard/s...d.php?t=788602 93 K1500 Short Step, 350, NV4500, EBL flash ECU. Vortec heads & roller cam someday... 05 Jeep Wrangler Unlimited. 3” lift & 6-speed 02 E320 the insurance total “free car” 13 Tahoe LTZ

01-27-2009, 10:56 PM	#3
big_al_71 Registered User Join Date: Jun 2008 Location: South Florida Posts: 11,375	Re: Fans - clutch vs. fixed? Off topic, Mike why not just switch to an electric fan? in the hot florida sun all my vehicles I always have switched to electric fans they cool so much better. __________________ Get your facts first, and then you can distort them as much as you please!!!!!. Sylvester's build thread >>>http://67-72chevytrucks.com/vboard/s...ht=big+rebuild

01-28-2009, 10:59 AM	#4
chris71 Registered User Join Date: Oct 2007 Location: Sykesville MD Posts: 357	Re: Fans - clutch vs. fixed? mike i have a fixed fan that i got off of a suburban , and i have no cooling issues even with an old rad. if the clutch on the fan is leaking a greasy-like fluid, it needs to be replaced. the purpose of a fan clutch from my understanding is to engage/dis-engage the spinning of the fan when it is needed or not needed. at start-up and highway, the clutch is not engaged and the fan will not spin as much, i supose to free up some of the stress that the motor uses to spin the fan, freeing up more hp i suppose. the thermostatic coil on the outside of the clutch moves the clutch fluid on the inside to make the fan spin or slow down. okay, i just found this, this should help. http://en.wikipedia.org/wiki/Fan_clutch also if that bi-metal coil is broken or missing, you should replace __________________ '55 3100 2nd series short-bed stepside '70 Corvette coupe stingray '71 Chevelle 2-dr coupe SS clone '71 C10 long-bed fleetside '83 long-haired brunette wife

01-28-2009, 11:18 AM	#5
50MOTORHEAD Registered User Join Date: Nov 2008 Location: midwest Posts: 113	Re: Fans - clutch vs. fixed? The trouble with most fixed blade fans is that they usually sound like a jet taking off,,,,all the time. My 67 had a 6 blade ,flex fan. MAN,,you talk about loud !!-KB

01-28-2009, 11:21 AM	#6
Sinister Between Trucks... Join Date: Mar 2002 Location: Los Angeles, CA. Posts: 3,830	Re: Fans - clutch vs. fixed? I've got a nylon flex fan, quiet and keeps my 350 at 190* __________________ Beat it to fit, Paint it to match...

01-28-2009, 11:40 AM	#7
chris71 Registered User Join Date: Oct 2007 Location: Sykesville MD Posts: 357	Re: Fans - clutch vs. fixed? be careful if you are shopping for used original fans, i have heard many stories of fan blades going through hoods because the rivets were compromised in some way. i.e. some rivets were missing, cracked blades, etc. __________________ '55 3100 2nd series short-bed stepside '70 Corvette coupe stingray '71 Chevelle 2-dr coupe SS clone '71 C10 long-bed fleetside '83 long-haired brunette wife

01-28-2009, 04:52 PM	#8
msgross Registered User Join Date: Jul 2006 Location: Central PA Posts: 12,201	Re: Fans - clutch vs. fixed? I have heard that about the flew fans... My original fan is a little rusty but seems to spin ok... It does have a slight amount of oil on the shaft but nothing bad for a 40 year old fan... My hesitation in going with the fixed fan is a slight loss of power and the constant noise. If I see that my clutch fan isn't cooling enough then i'll just replace the clutch... thanks for the tips guys... __________________ The Garage: 1968 K-10 SWB - "Project Money Pit" 1996 Z-71 - "huntin rig" 1969 C-10 LWB (SOLD) "Project flip that truck or else" 1993 Passport, F@rd 1-ton (SOLD)"Project Cousin Eddie" My Garage Build "The 1,000 footer"

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