Fan clutch how to tell if its good or bad - The 1947 - Present Chevrolet & GMC Truck Message Board Network

CG · 08-01-2021, 07:38 PM

Finally getting around to putting everything back together after I changed my water pump a while ago. 1971 402 with air ... Before I toss the fan back on how do I tell if the fan clutch is working properly? I hope its a mechanical "feel" thing, not I have to put it all back together and run it thing.

jimijam00 · 08-01-2021, 07:45 PM

If it worked when you took it off, I'm going to guess that it still works. Shake the hell out of it and listen for anything inside rattling around.

CG · 08-01-2021, 07:46 PM

I have no idea if it worked when I took it off. I bought the truck with a very bad water pump bearing.

**special-K** · 08-01-2021, 08:35 PM

It should resist spinning freely.

**Steeveedee** · 08-01-2021, 09:17 PM

Put it on and run it. Tim's right about the loose feel, though. But it can be hard to tell until you install it. FWIW, a worn clutch can lead to a bad water pump bearing due to the fan wobbling. If you haven't already degreased it, show us a picture of the shaft where it comes out of the clutch. We may be able to get something out of that picture.

72c20customcamper · 08-01-2021, 09:54 PM

Loose spin like Tim said . I had one that did the opposite thing. It was always engaged I thought I blew something one day as it started to roar and did not stop. I must have looked around the truck three or four times before I suspected the clutch. 20 minute job to replace and fairly cheap.

68Gold/white · 08-02-2021, 02:10 AM

Mount it on the water pump. See if it spins too freely, as mentioned. Grab a fan blade, see if the blade/fan clutch housing has any movement, forward or backwards (should be none). If it looks like it has leaked any oil, it’s no good.

Then test drive it, if it passed these tests. I’ve got an old one I bought from member here, hope it is good, also.

**Getter-Done** · 08-02-2021, 06:35 AM

Same as above on the clutch.
Visual Check on the rivets of the fan.
Also cracks in the blades.

.....

**Stocker** · 08-02-2021, 08:36 AM

There should be no leakage at the shaft. Bolt it into place -- the shaft should have no wobble. Rotate the fan and it should feel like it's mired in molasses.

Thundarr · 08-02-2021, 08:46 AM

What about using a heat gun (or hair dryer) to heat up the element to check that the internal clutch engages?

CG · 08-02-2021, 05:01 PM

Visually everything looks good per everyone's direction. Physically it doesnt free wheel, it sluggishly wheels. I'm going to go ahead and install and hope for the best. Thanks for everyone's input.

**Stocker** · 08-02-2021, 07:21 PM

The worst that can happen is you might have to replace it with a new one..... not a huge deal.

Oh by the way, are you (or will you be) using a stud kit? I hadn't heard of that when I did mine, but it should make R&R a bit easier.

**MJN** · 08-03-2021, 08:03 AM

Heres more of the same as posted above
https://www.haydenauto.com/en/techni...q-fan-clutches

72c20customcamper · 08-03-2021, 09:26 AM

Quote:

Originally Posted by Stocker

The worst that can happen is you might have to replace it with a new one..... not a huge deal.

Oh by the way, are you (or will you be) using a stud kit? I hadn't heard of that when I did mine, but it should make R&R a bit easier.

I do the studs on every vehicle I own makes it so much easier .

08-01-2021, 07:38 PM	#1
CG BlahBlahBlah Join Date: Feb 2002 Location: Monroe, Wa. Posts: 19,772	Fan clutch how to tell if its good or bad Finally getting around to putting everything back together after I changed my water pump a while ago. 1971 402 with air ... Before I toss the fan back on how do I tell if the fan clutch is working properly? I hope its a mechanical "feel" thing, not I have to put it all back together and run it thing. __________________ … … … … … … … … ... … … … … … … … … … … … Monroe Swap meet May 18-19. Mike has the same spots for the NW guys he's had forever. Lunch time BBQ at the spaces. If you have stuff to sell bring it along. If you have a question PM stllookn (Mike) here via the board. https://67-72chevytrucks.com/vboard/...d.php?t=851291

08-01-2021, 07:45 PM	#2
jimijam00 Registered User Join Date: Apr 2009 Location: PNW Posts: 553	Re: Fan clutch how to tell if its good or bad If it worked when you took it off, I'm going to guess that it still works. Shake the hell out of it and listen for anything inside rattling around.

08-01-2021, 07:46 PM	#3
CG BlahBlahBlah Join Date: Feb 2002 Location: Monroe, Wa. Posts: 19,772	Re: Fan clutch how to tell if its good or bad I have no idea if it worked when I took it off. I bought the truck with a very bad water pump bearing. __________________ … … … … … … … … ... … … … … … … … … … … … Monroe Swap meet May 18-19. Mike has the same spots for the NW guys he's had forever. Lunch time BBQ at the spaces. If you have stuff to sell bring it along. If you have a question PM stllookn (Mike) here via the board. https://67-72chevytrucks.com/vboard/...d.php?t=851291

08-01-2021, 08:35 PM	#4
special-K Special Order Join Date: Nov 2004 Location: Mt Airy, MD Posts: 85,863	Re: Fan clutch how to tell if its good or bad It should resist spinning freely. __________________ "BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~

08-01-2021, 09:17 PM	#5
Steeveedee Who Changed This? Join Date: Jan 2013 Location: Simi Valley, CA Posts: 10,086	Re: Fan clutch how to tell if its good or bad Put it on and run it. Tim's right about the loose feel, though. But it can be hard to tell until you install it. FWIW, a worn clutch can lead to a bad water pump bearing due to the fan wobbling. If you haven't already degreased it, show us a picture of the shaft where it comes out of the clutch. We may be able to get something out of that picture. __________________ ~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA

08-01-2021, 09:54 PM	#6
72c20customcamper Registered User Join Date: Jul 2018 Location: Catskill Mountains,NY Posts: 8,139	Re: Fan clutch how to tell if its good or bad Loose spin like Tim said . I had one that did the opposite thing. It was always engaged I thought I blew something one day as it started to roar and did not stop. I must have looked around the truck three or four times before I suspected the clutch. 20 minute job to replace and fairly cheap. __________________ Mark 72 c20 custom camper Husky edition, 66 SS396 Chevelle 1964 Hawk, 63 Avanti,62 lark 1969 AMX , 1968 c20 stepside ,85 K20 1977 Suburban sold 68 anniversary.

08-02-2021, 02:10 AM	#7
68Gold/white Registered User Join Date: Sep 2011 Location: Ark City, Kansas Posts: 3,271	Re: Fan clutch how to tell if its good or bad Mount it on the water pump. See if it spins too freely, as mentioned. Grab a fan blade, see if the blade/fan clutch housing has any movement, forward or backwards (should be none). If it looks like it has leaked any oil, it’s no good. Then test drive it, if it passed these tests. I’ve got an old one I bought from member here, hope it is good, also. Last edited by 68Gold/white; 08-02-2021 at 02:11 AM. Reason: Cheese whiz

08-02-2021, 06:35 AM	#8
Getter-Done Senior Member Join Date: Dec 2009 Location: TN. Posts: 7,719	Re: Fan clutch how to tell if its good or bad Same as above on the clutch. Visual Check on the rivets of the fan. Also cracks in the blades. ..... __________________ ________________________________________________________________________________________ ____________________________________________ 84 Chevy K-20 63 Impala (my high school car) http://67-72chevytrucks.com/vboard/s...Crew Cab Build

08-02-2021, 08:36 AM	#9
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,495	Re: Fan clutch how to tell if its good or bad There should be no leakage at the shaft. Bolt it into place -- the shaft should have no wobble. Rotate the fan and it should feel like it's mired in molasses. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

08-02-2021, 08:46 AM	#10
Thundarr Registered User Join Date: May 2013 Location: Coppell, Texas Posts: 176	Re: Fan clutch how to tell if its good or bad What about using a heat gun (or hair dryer) to heat up the element to check that the internal clutch engages? __________________ 1971 GMC C15 Sierra Grande SWB 1972 Chevy C10 Custom Deluxe LWB 2018 GMC Yukon Denali

08-02-2021, 05:01 PM	#11
CG BlahBlahBlah Join Date: Feb 2002 Location: Monroe, Wa. Posts: 19,772	Re: Fan clutch how to tell if its good or bad Visually everything looks good per everyone's direction. Physically it doesnt free wheel, it sluggishly wheels. I'm going to go ahead and install and hope for the best. Thanks for everyone's input. __________________ … … … … … … … … ... … … … … … … … … … … … Monroe Swap meet May 18-19. Mike has the same spots for the NW guys he's had forever. Lunch time BBQ at the spaces. If you have stuff to sell bring it along. If you have a question PM stllookn (Mike) here via the board. https://67-72chevytrucks.com/vboard/...d.php?t=851291

08-02-2021, 07:21 PM	#12
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,495	Re: Fan clutch how to tell if its good or bad The worst that can happen is you might have to replace it with a new one..... not a huge deal. Oh by the way, are you (or will you be) using a stud kit? I hadn't heard of that when I did mine, but it should make R&R a bit easier. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

08-03-2021, 08:03 AM	#13
MJN Registered User Join Date: Feb 2000 Location: Maquoketa, Ia/ Orr, Mn Posts: 2,961	Re: Fan clutch how to tell if its good or bad Heres more of the same as posted above https://www.haydenauto.com/en/techni...q-fan-clutches __________________ '51 South Bend Model "9A" '56 Chevy 3600 NAPCO '74 Chevy Cheyenne Super K20-restored on 37's '72 GMC Sierra Custom K2500- in progress '08 GMC Envoy Denali '12 GMC Sierra 2500HD Denali '17 GMC Yukon XL VCCA member #58596 http://www.nohrco.com



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