Clutch Fan Replacement - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**samkost** · 08-14-2016, 06:59 PM

How do I know when it is time to replace/rebuild my clutch fan on my 72' C10?
Wondering what are the tell tail signs that it needs replacing.
I have a 1/2 ton, with 350/350 TH and an air conditioned cab.
Truck runs perfectly and cool.
Local parts store shows a non thermal replacement?
Any recomedation for a certain brand of part and info for replacing would be appreciated.

Mike C · 08-14-2016, 07:08 PM

With engine turned off, grab the fan and spin it. If it stops pretty much as soon as you let go it's fine. If it spins around more than one revolution, it's probably whooped.

For replacement I am a fan of the Thermostatically controlled fan. Worth the extra $.

**Stocker** · 08-14-2016, 07:25 PM

^^ What he said. It should have resistance to turning by hand, as if it's mired in molasses. Also look for any sign of fluid leaking out, or any wobble where the shaft meets the clutch.

Definitely get a thermal unit, not a non-thermal.

Mine still works okay but it has lost a tiny amount of fluid and the shaft has a very small amount of play, so I'm gonna replace it before long. Considering an AC Delco unit, though I haven't really heard anything bad about other brands. I'm trying to buy USA-made and avoid Chinese, but it's been virtually impossible to figure out where they are built. I also want a heavy-duty unit (explained & illustrated in the Hayden link below) but that info is also hard to come by.

Couple of helpful sites:

http://www.haydenauto.com/featured%2...s/content.aspx

http://www.aa1car.com/library/cooling_fan_clutch.htm

**samkost** · 08-14-2016, 07:34 PM

Thanks guys,
From what you guys described it time for replacement.
Now to find a quality Good ole USA part.
Thanks again,
Sam

tdangle · 08-14-2016, 07:37 PM

Typically you will see starting to get hot when idling or slow traffic around town, but as soon as you get up to 30+ MPH the engine cools down right away. It's all a matter of air flow thru the radiator. At low speeds and higher temps the fan will lock up and pull air. At higher speeds the fan is not really needed, as air flow thru the grill is enough to cool.

That is basically the difference between thermal and non-thermal fan clutches. the non thermal will lock up at low speeds and release at higher engine speeds. The thermal units add temperature sensing to only lock up at lower speeds when the airflow temp reaches a certain point.

A lot less common failure (if you could call it that) is that the unit wants to lock up all the time. It will sound like you are driving around in a lower gear with all the noise from the fan.

Don't over think it. if everything is working well for you, wait for a failure. I've had clutch fans last years and years before failing.

**Stocker** · 08-15-2016, 03:27 PM

Quote:

Originally Posted by samkost

Thanks guys,
From what you guys described it time for replacement.
Now to find a quality Good ole USA part.

Just bought mine at NAPA and it's made in Lewisville, TX by Four Seasons. HTH

**samkost** · 08-15-2016, 06:20 PM

Tom,
Is the Delco clutch fan you have, a thermal or non-thermal?
I made a similar post about replacing mine and wonder if the part you have is a direct replacement. Forum members answered suggesting that I get a thermal style for replacement.
Thanks
Sam

**samkost** · 08-15-2016, 06:26 PM

Oops,

my mistake,my question above should have gone to anther post.

08-14-2016, 06:59 PM	#1
samkost Senior Member Join Date: Sep 2014 Location: Lake Tapps, Wa. Posts: 625	Clutch Fan Replacement How do I know when it is time to replace/rebuild my clutch fan on my 72' C10? Wondering what are the tell tail signs that it needs replacing. I have a 1/2 ton, with 350/350 TH and an air conditioned cab. Truck runs perfectly and cool. Local parts store shows a non thermal replacement? Any recomedation for a certain brand of part and info for replacing would be appreciated.

08-14-2016, 07:08 PM	#2
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,715	Re: Clutch Fan Replacement With engine turned off, grab the fan and spin it. If it stops pretty much as soon as you let go it's fine. If it spins around more than one revolution, it's probably whooped. For replacement I am a fan of the Thermostatically controlled fan. Worth the extra $. __________________ 44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax

08-14-2016, 07:25 PM	#3
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,595	Re: Clutch Fan Replacement ^^ What he said. It should have resistance to turning by hand, as if it's mired in molasses. Also look for any sign of fluid leaking out, or any wobble where the shaft meets the clutch. Definitely get a thermal unit, not a non-thermal. Mine still works okay but it has lost a tiny amount of fluid and the shaft has a very small amount of play, so I'm gonna replace it before long. Considering an AC Delco unit, though I haven't really heard anything bad about other brands. I'm trying to buy USA-made and avoid Chinese, but it's been virtually impossible to figure out where they are built. I also want a heavy-duty unit (explained & illustrated in the Hayden link below) but that info is also hard to come by. Couple of helpful sites: http://www.haydenauto.com/featured%2...s/content.aspx http://www.aa1car.com/library/cooling_fan_clutch.htm __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay Last edited by Stocker; 08-14-2016 at 07:49 PM.

08-14-2016, 07:34 PM	#4
samkost Senior Member Join Date: Sep 2014 Location: Lake Tapps, Wa. Posts: 625	Re: Clutch Fan Replacement Thanks guys, From what you guys described it time for replacement. Now to find a quality Good ole USA part. Thanks again, Sam

08-14-2016, 07:37 PM	#5
tdangle Registered User Join Date: Mar 2005 Location: Jurupa Valley, Ca Posts: 1,210	Re: Clutch Fan Replacement Typically you will see starting to get hot when idling or slow traffic around town, but as soon as you get up to 30+ MPH the engine cools down right away. It's all a matter of air flow thru the radiator. At low speeds and higher temps the fan will lock up and pull air. At higher speeds the fan is not really needed, as air flow thru the grill is enough to cool. That is basically the difference between thermal and non-thermal fan clutches. the non thermal will lock up at low speeds and release at higher engine speeds. The thermal units add temperature sensing to only lock up at lower speeds when the airflow temp reaches a certain point. A lot less common failure (if you could call it that) is that the unit wants to lock up all the time. It will sound like you are driving around in a lower gear with all the noise from the fan. Don't over think it. if everything is working well for you, wait for a failure. I've had clutch fans last years and years before failing. __________________ Terry 1970 Custom Camper/C20 , GM Crate 350/7004R, Dana 60, factory AC

08-15-2016, 06:20 PM	#7
samkost Senior Member Join Date: Sep 2014 Location: Lake Tapps, Wa. Posts: 625	Re: Clutch Fan Replacement Tom, Is the Delco clutch fan you have, a thermal or non-thermal? I made a similar post about replacing mine and wonder if the part you have is a direct replacement. Forum members answered suggesting that I get a thermal style for replacement. Thanks Sam

08-15-2016, 06:26 PM	#8
samkost Senior Member Join Date: Sep 2014 Location: Lake Tapps, Wa. Posts: 625	Re: Clutch Fan Replacement Oops, my mistake,my question above should have gone to anther post.



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