engine fans revisited
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Senior User
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You will hear it, especially when accelerating from a stop. The fan will always turn but not at the same speed as the engine when decluthched. If you are unsure if it declutching compare the stiffness when the engine is dead cold and after you have driven at normal temps. The fan on a cold engine will be much stiffer than after running for a while as it is clutched in on a cold engine. A NAPA clutch can take 10 minutes, of actual driving, to declutch.
Ron W.
Ron W.
Junior User
Joined: Jan 2006
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From: Troy New York
I still am not sure about it. If you listen to a big truck you hear nothing, then when the engages, it makes one hell of a noise. It was 25 degrees this morning and my fan was running. I have never seen it not spin. It always seems to spin with the engine, even though it does. Why is it not like a tractor trailer fan. Engaged and loud, or disengaged and no noise.
Post Fiend
Joined: Feb 2006
Posts: 11,892
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From: Middle Tennessee
Originally Posted by cookie88
The stock fan with the clutch fully engaged moves something like 7500 cfm. That, from what I understand, equates to almost 50 horsepower. Definitely enough for you to feel the difference.
Perhaps that is why they never really unlock by design, so you wouldn't feel it locking as much. Imagine that on a test drive. How many others can really feel a performance hit when the fan clutch engages?
Cargo Master
Joined: Jan 2002
Posts: 2,079
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From: LA and CO
I was always taught that to check the fan clutch you dove it around to get it hot then stopped it and tried to rotate the fan. It should be hard to turn since the coupling should be locked. If it turns the same as when it's cold then it's bad.
I only noticed mine engaging during the hottest summer months down here in New Orleans. When I would take off from a stop it would be engaged then release.
Maybe if you never hear it it's because it's broken..... That's how my F150 was. I could never hear the "whoooosh" of it when it should've been engaged (hot). The truck always ran a little hot, so I changed the fan clutch. That's all that was wrong. Clutch was old and worn out, silicone fluid in it had leaked out.
Now, I did notice this. Once the new fan clutch was installed on my F150, it would be engaged whenever the truck was started cold. This is because the fluid in the clutch was all settled to the bottom. It would take less than a minute for the clutch to disengage, then it would function normal.
I never hear the fan engaged on my PSD, when it's cold... Maybe mine is bad too....
I only noticed mine engaging during the hottest summer months down here in New Orleans. When I would take off from a stop it would be engaged then release.
Maybe if you never hear it it's because it's broken..... That's how my F150 was. I could never hear the "whoooosh" of it when it should've been engaged (hot). The truck always ran a little hot, so I changed the fan clutch. That's all that was wrong. Clutch was old and worn out, silicone fluid in it had leaked out.
Now, I did notice this. Once the new fan clutch was installed on my F150, it would be engaged whenever the truck was started cold. This is because the fluid in the clutch was all settled to the bottom. It would take less than a minute for the clutch to disengage, then it would function normal.
I never hear the fan engaged on my PSD, when it's cold... Maybe mine is bad too....
Last edited by John7894; Oct 28, 2006 at 09:21 AM.
Fleet Owner
Joined: Jun 2004
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From: Rio Rico, AZ.
Originally Posted by John7894
I never hear the fan engaged on my PSD, when it's cold... Maybe mine is bad too....
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On a semi truck the fan is engaged by an air switch. Completely different from a pickup. A semi's fan doesn't spin until the air switch locks in the clutch. On most semi trucks the driver can manually lock in the fan with a switch in the cab. I would lock mine in before climbing steep hills. Helped to keep the engine a little cooler running.
On checking the fan by hand, I too was under the impression that it would be stiffer after running, which may be true for other types of clutches. I found out though that with the fluid coupling type the exact opposite is true, unless you shut the engine off while the fan was engaged. OEM clutches disengage much quicker than NAPA/Haynes clutches.
Ron W.
On checking the fan by hand, I too was under the impression that it would be stiffer after running, which may be true for other types of clutches. I found out though that with the fluid coupling type the exact opposite is true, unless you shut the engine off while the fan was engaged. OEM clutches disengage much quicker than NAPA/Haynes clutches.
Ron W.
Junior User
Joined: Jan 2006
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From: Troy New York
what year was your F-150? how many miles? Isn't the clutch supposed to be changed every certain amount of miles. Say 50K, thats alot of spinning.
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Post Fiend
Joined: Feb 2006
Posts: 11,892
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From: Middle Tennessee
My truck has never come even close to running hot, and it get's hot here. I have never noticed it cycling so it might be stuck engaged, or I'm not really paying attention. It is not something I am going to worry about over the winter.
Now I did notice in my new Jegs catalog that flex-a-lite has a dual electric fan setup for our trucks. Fully electric and variable control depending on temp/AC. But that rascal runs $500. Still, 50hp removed from the pulley made up for at the alternator with a pull of 28-36 amps. It is rated at 6k CFM. Does anybody know what that kind of electrical load equates to in HP?
Now I did notice in my new Jegs catalog that flex-a-lite has a dual electric fan setup for our trucks. Fully electric and variable control depending on temp/AC. But that rascal runs $500. Still, 50hp removed from the pulley made up for at the alternator with a pull of 28-36 amps. It is rated at 6k CFM. Does anybody know what that kind of electrical load equates to in HP?
Elder User
Joined: Oct 2006
Posts: 600
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From: Albuquerque, NM
I'm like Tennessee, me truck has never even been close to heating up even when pulling long hills with a camper and boat. I never notice my fan cycling. I'm gonna have to re-read this whole thing again and see if I can figure out what everyone is saying. So the fan should be engaged in the morning because the liquid in the clutch is cold and then should warm up fairly quickly and not pull or engage again unless the engine heats up and needs additional cooling? So I should be able to turn the fan with little resistance after the engine comes up to NOT? I'm confused now.
Fleet Owner
Joined: Jun 2004
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From: Rio Rico, AZ.
Originally Posted by rad1026
I'm like Tennessee, me truck has never even been close to heating up even when pulling long hills with a camper and boat. I never notice my fan cycling. I'm gonna have to re-read this whole thing again and see if I can figure out what everyone is saying. So the fan should be engaged in the morning because the liquid in the clutch is cold and then should warm up fairly quickly and not pull or engage again unless the engine heats up and needs additional cooling? So I should be able to turn the fan with little resistance after the engine comes up to NOT? I'm confused now.
I have a recording that I made a while back, mostly to showcase how much I like the sound of my turbo with the Wicked Wheel installed. But you can hear the fan engage about halfway through the recording.
I made the recording while pulling aprox 4% grade with the 13k 5th wheel.
I can make it come on at will if I am going up a mountain pass and floor the throttle empty.
In the hot desert SW region with the AC on it will stay on all the time driving empty and on a level road at 65 mph.
http://home.comcast.net/~kwikkordead/Wicked_Wheel.mp3
Elder User
Joined: Oct 2006
Posts: 600
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From: Albuquerque, NM
I guess I need to just turn the music off and listen a little more to the truck. I like the wicked wheel sound. I can't really hear my turbo spooling up and I don't have a boost guage yet to tell me when to listen. I'm new, I'm learning. I'll keep asking questions.
Post Fiend
Joined: Feb 2006
Posts: 11,892
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From: Middle Tennessee
Well that explains it, I must be going deaf because I did not hear it on that clip. Too many rifle ranges and trips in aircraft and gunfire incidents without earplugs or something. Does it come with a butt-o-meter feel too when it locks up?