Fan clutch

[Bingo]

Hey so i noticed over last year i can hear the fan on all time when i start the truck and drive it. Doesn't matter what temperature it is it always seems to be on and i can hear it inside the cab. Educate me here please, when are these suppose to be on. I figured it was bad so i swapped it at the weekend for a 2022 one off a low mileage truck. However it seems exactly the same.

 

[mands0807]

Hey so i noticed over last year i can hear the fan on all time when i start the truck and drive it. Doesn't matter what temperature it is it always seems to be on and i can hear it inside the cab. Educate me here please, when are these suppose to be on. I figured it was bad so i swapped it at the weekend for a 2022 one off a low mileage truck. However it seems exactly the same.

Fan clutch driven by the crank pulley, or electric fan for the a/c?

 

[Bingo]

The one attached to the water pump/pulley is the one i mean. The ac isn't on at this point and turning all heater ,a/c on or off does not effect the noise.

 

[crackerjack1957]

Hey so i noticed over last year i can hear the fan on all time when i start the truck and drive it. Doesn't matter what temperature it is it always seems to be on and i can hear it inside the cab. Educate me here please, when are these suppose to be on. I figured it was bad so i swapped it at the weekend for a 2022 one off a low mileage truck. However it seems exactly the same.

You should be looking at the electrical fan instead of the mechanical fan.
Electric fan stays on all the time if AC or Def is selected if its working properly.

 

[Bingo]

I can hear fan over engine regardless of whether anything is on ( which most of time its not)

 

[Grams]

That mechanical fan is (on most) mounted to a viscous-clutch. That clutch engages when high temperatue ….AIR temperature…. is sensed.

There are times when, during normal operations, that clutch will engage and the fan-noise will become quite noticeable. This is normal, and when the coolant in the radiator temperature decreases…the air flowing THRU the radiation will also decrease….the clutch will sense that lowered temp…and allow the fan to again “free-wheel”.

If you wish to test that clutch….when the engine is COOL (perhaps at first start-up of the day)…. using a large rag or old towel as a glove (to protect your hends)… reach-in to apply ressistance to the fan blades as they rotate. At engine idle you should be able to stop the blades completely.
At HOT temps…the blades will be almost impossible to stop rotation…if the viscous clutch is operating correctly.

My 2012 4.7L V8 almost overheated when I believed it shouldn’t be straining durig a long tow up a mild slope. I used the method above to find that the viscous clutch was free-wheeling continuously regardless of engine and coolant temp.

I replaced that clutch with a lifetime warrantied one from AutoZone…(beware…it’s LEFT-HAND THREADS) ….. and it solved the problem completely.

Hope this helps.

 

[crackerjack1957]

I can hear fan over engine regardless of whether anything is on ( which most of time its not)

If you hear a fan while idling......it cannot be the mechanical fan.

 

[Bingo]

Just for clarification. When i turn the truck on (today -2c) cold it instantly roars so loud i cant even hear the engine. If you guys are saying its not the fan clutch which i just replaced ( and made no difference) what should i be looking at?
thanks

 

[Grams]

It may be that your viscous clutch has failed in the “engaged” position. You can test that, again, with a rag in your hand to see if you can bring the fan to a stop or not.
In this case, of it being engaged even when “cold”…. you should be able (with a healthy clutch) …be able to hold the blades while someone starts the engine…and it should be relatively easy to prevent the blades from turning if the clutch is not engaged.

(Be aware that some “shade-tree” mechanics have been known to drive a screw through the clutch-housing to delibertely and permanently “lock up” that clutch such that the fan turns continuously. If a clutch is locked up it will be hazardous to attempt holding that fan from rotating.)

 

[Wild one]

Just for clarification. When i turn the truck on (today -2c) cold it instantly roars so loud i cant even hear the engine. If you guys are saying its not the fan clutch which i just replaced ( and made no difference) what should i be looking at?
thanks

It'll be loud on start up when it's cold,as the fluid inside the clutch is cold and stiff. When my 14 still had the mechanical fan on it,it'd roar to beat hell at temps below 0C until the truck had made a couple KMs.I think you're worrying about nothing.
Take Grams advice with a whole lot of salt,as i wouldn't be grabbing a fan on a running engine,even with my thick welding gloves,you're better off wiggling it,and spinning it with the engine off,alot less chance of losing fingers that way

 

[Grams]

It'll be loud on start up when it's cold,as the fluid inside the clutch is cold and stiff. When my 14 still had the mechanical fan on it,it'd roar to beat hell at temps below 0C until the truck had made a couple KMs.I think you're worrying about nothing.
Take Grams advice with a whole lot of salt,as i wouldn't be grabbing a fan on a running engine,even with my thick welding gloves,you're better off wiggling it,and spinning it with the engine off,alot less chance of losing fingers that way

 

[Bingo]

One more note here my main point is it never used to do this till the last 12 mths, im also pretty sure it stays on too even after a few mins

 

[Wild one]

One more note here my main point is it never used to do this till the last 12 mths, im also pretty sure it stays on too even after a few mins

Check it when it's cold by wiggling it and turning it,it should have a bit of resistance to turning,then check it again when the trucks good and hot,it should have a bit more resistance to turning when the truck is at full operating temp. Are you sure you're just not tuned into it more now then you used to be,especially now that the weather is getting colder

 

[Bingo]

i will check today but it def never used to do it atall and has been doing it through the summer too