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Cooling fan BLASTS at start-up

ErikTheRed

ErikTheRed

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Something Ive noticed with my new truck that seems completely bass-ackwards. When I start the truck from cold, the cooling fan howls like mad. As the truck warms up, usually after just a cpl minutes, the fan disengages and the howl goes away. I never hear the fan again after that no matter how warm the outside temp or how much driving/towing I do, and the ECT stays put. Is this normal? Why is the fan running like crazy when its not needed, but is totally silent when I'd expect it to be running?
 
ErikTheRed said:
Something Ive noticed with my new truck that seems completely bass-ackwards. When I start the truck from cold, the cooling fan howls like mad. As the truck warms up, usually after just a cpl minutes, the fan disengages and the howl goes away. I never hear the fan again after that no matter how warm the outside temp or how much driving/towing I do, and the ECT stays put. Is this normal? Why is the fan running like crazy when its not needed, but is totally silent when I'd expect it to be running?
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That’s normal for an engine driven clutch fan. The viscous fluid is thick when cold and that causes the fan to turn until it has a chance to warm up a bit runs out of the proper chamber when it’s parked and has to spin to go back where it belongs to release the clutch.

(Hat tip to @johnmyster for the detail correction)
 
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jsalbre said:
That’s normal for an engine driven clutch fan. The viscous fluid is thick when cold and that causes the fan to turn until it has a chance to warm up a bit.
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Yessir, I understand how the clutch fan works. Many of my vehicles past and present have/had them. But Ive never experienced the raging full-on howl at start-up as I get with this truck. If it were just a matter of the mechanical/fluid characteristics of the clutch fan, then all of my viscous fluid fan clutch-equipped vehicles would act the same. They don't. So Im curious of others with the same engine/fan are experiencing the same issue, and if so, then I can determine its normal operation for these vehicles.
 
ErikTheRed said:
Yessir, I understand how the clutch fan works. Many of my vehicles past and present have/had them. But Ive never experienced the raging full-on howl at start-up as I get with this truck. If it were just a matter of the mechanical/fluid characteristics of the clutch fan, then all of my viscous fluid fan clutch-equipped vehicles would act the same. They don't. So Im curious of others with the same engine/fan are experiencing the same issue, and if so, then I can determine its normal operation for these vehicles.
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Perhaps your other trucks had a lesser cooling system that moved less air.

The 19+ Ram Cummins howls, they all do it. It's a manly man fan.
 
ErikTheRed said:
Yessir, I understand how the clutch fan works. Many of my vehicles past and present have/had them. But Ive never experienced the raging full-on howl at start-up as I get with this truck. If it were just a matter of the mechanical/fluid characteristics of the clutch fan, then all of my viscous fluid fan clutch-equipped vehicles would act the same. They don't. So Im curious of others with the same engine/fan are experiencing the same issue, and if so, then I can determine its normal operation for these vehicles.
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Every vehicle I’ve ever owned with a viscous fluid fan clutch, *including* two current-generation HD Rams, has done exactly this.

Searching “viscous fluid fan clutch loud when cold” on Google or your search engine of choice will return hundreds of pages stating exactly this.
 
Well, I DO like a manly-man fan, sooo.... I'm going with normal operation. :)

1994 Jeep Cherokee 5.2, 1997 Chevy 1500 5.7, 1995 Ford F350 7.5, 2006 Ram 2500 5.9... none of them made this sort of fan racket at start-up. But I'm cool with it if thats just what these things do.
 
ErikTheRed said:
1994 Jeep Cherokee 5.2, 1997 Chevy 1500 5.7, 1995 Ford F350 7.5, 2006 Ram 2500 5.9... none of them made this sort of fan racket at start-up. But I'm cool with it if thats just what these things do.
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It’s called “morning sickness” and while all those other rigs listed should have done the same thing one of them had the same fan, and none of them moved as much air, so the sound is very different. The 06 5.9 had a very similar fan clutch and fan and would have been closet to having a similar sound at cold startup.
 
It has nothing to do with the viscosity of the silicone fluid. It has everything to do with the truck being parked, and the fluid settling back into the chamber between the fan body and the shaft...coupling the two. The fan needs to spin to drive the fluid back out of the chamber, thus decoupling the clutch.
 
johnmyster said:
It has nothing to do with the viscosity of the silicone fluid. It has everything to do with the truck being parked, and the fluid settling back into the chamber between the fan body and the shaft...coupling the two. The fan needs to spin to drive the fluid back out of the chamber, thus decoupling the clutch.
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You’re correct. I went and re-educated myself. Some point over the years my brain edited that knowledge to something that sounded plausible but wasn’t quite accurate.
 
Does this usually go away in a few minutes for you guys? I remember on my '17 Cummins the fan seemed full blast all the time no matter what. Sounded like a jet and you could feel the air blowing out of the hood/fender gaps Really hard. The dealer said they're one speed fans and it was supposed to always do that.
 
Forceofwill said:
Does this usually go away in a few minutes for you guys? I remember on my '17 Cummins the fan seemed full blast all the time no matter what. Sounded like a jet and you could feel the air blowing out of the hood/fender gaps Really hard. The dealer said they're one speed fans and it was supposed to always do that.
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You were lied to. The fan clutches are electronically controlled viscous clutches and are defiantly not one speed.
 
Forceofwill said:
Does this usually go away in a few minutes for you guys? I remember on my '17 Cummins the fan seemed full blast all the time no matter what. Sounded like a jet and you could feel the air blowing out of the hood/fender gaps Really hard. The dealer said they're one speed fans and it was supposed to always do that.
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Depending on the specifics of the clutch and fan, most clutches spin at about 20% shaft speed uncoupled and 80% when coupled.

Mine cycles the fan at idle if the A/C is running and it's hot, because it knows there's not any natural airflow over the condenser due to vehicle movement. It also cycles the fan sometimes due to intercooler load, despite ECTs being normal. There seem to be a few "triggers" for fan operation aside from ECT setpoint.

Mine is actually uncoupled at cold start...it doesn't suffer the normal leakback that I alluded to earlier. Yours was full time coupled when it shouldn't have been.
 
The only time mine will do that is if I have the A/C on before I start driving it. I feel it has more to do with the refrigerant pressures than anything once the air gets flowing through the condenser it settles down
 
AH64ID said:
It’s called “morning sickness” and while all those other rigs listed should have done the same thing one of them had the same fan, and none of them moved as much air, so the sound is very different. The 06 5.9 had a very similar fan clutch and fan and would have been closet to having a similar sound at cold startup.
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Makes sense. I actually had to replace the fan clutch on my 06 5.9 because it eventually stopped engaging at all, and the ECT would climb like crazy, especially towing. With the replacement fan clutch, ECT was much better managed but still didn't make the start-up tornado sounds. Like you said, there are differences in the sheer amount of air the new system moves compared the old, so yeah, I supposed it'd be noisier even though everything is working as designed.

jsalbre said:
If it was going full time it was broken. It should only last a minute or so.
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Thats about how long it takes-- a minute, maybe 90 seconds and it shuts off almost like a light switch. It won't make that level of noise again no matter what the truck is doing, grocery-getting or towing 12k up an 8% climb.
 
johnmyster said:
It has nothing to do with the viscosity of the silicone fluid. It has everything to do with the truck being parked, and the fluid settling back into the chamber between the fan body and the shaft...coupling the two. The fan needs to spin to drive the fluid back out of the chamber, thus decoupling the clutch.
Click to expand...

This is kinda how my body works in the morning, the piss is coupled to the bladder and doesn't want to come out.

(actually, it's more due to the enlarged prostate restricting the peak flow rate)

Follow me for more old guy tips.
 
Brutal_HO said:
This is kinda how my body works in the morning, the piss is coupled to the bladder and doesn't want to come out.

(actually, it's more due to the enlarged prostate restricting the peak flow rate)

Follow me for more old guy tips.
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Can you bolt on a new one?
 
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