So sometimes when I'm towing (5,000+ lbs) the aux engine fan will kick on and off randomly...whats weird is that it happens sometimes right away, and sometimes it waits till the engine starts to get hot, if I'm haulin up a steep grade for a while. So my question is, is there a set temp that the fan should always come on at, or does it happen due to some other trigger? It's a 2006 5.7l 4wd.

 

Um, Aux engine fan? As far as I know there is only a single Fluid clutch driven fan which will catch up to engine speed as the clutch heats up. This is always somewhat engaged, However, There is no specified set temperature for it to be fully engaged.

Short of mods, The only other cooling fan I know of is the AC condenser fan which comes on and off with the AC clutch.

Unless the cooling setup is not stock.

 

AC fan?

 

As said, the only two OEM fans you have is the AC fan which should be running any time the AC is on and the clutch fan. So I think you need to be a bit more clear on what you are saying or mean.

 

Ok that's part of what has me confused...so your saying one is an A/C fan? There are 2 fans down there, Ive looked a few times. Anyway, I can hear a fan kick on when im towing...it's loud, unmistakeable as anything other then a fan. And im not running the A/C when Im towing up a grade, so how can it be that.... Is it a tranny fan that kicks on to keep the temp down? I mean this thing sounds like a vaccum cleaner at full suck lol.

 

Do you have a CAI? Did you buy the truck used, Maybe someone added an Aux fan for the tranny cooler or something. Do you have Defrost on, Maybe the AC compressor is engaged for some reason and you don't realize it.

Like I said the one fan is pretty much always engaged, Infact it isn't even an electric fan, and the AC fan only turns on when compressor is engaged. Neither of them you should really be able to hear, Especially while driving.

One other idea, Check your tranny fluid. Sometimes if your a low the tranny will get pretty loud. Another thought is maybe there is a vacuum leak somewhere. You would hear this anytime the revs go up because the vacuum goes up.

 

Stock comes with a clutch fan mounted on the front of the engine and a electric fan mounted on the AC condensor coil on the drivers side. If yours is different than it has been modified. Post some pictures.

 

Agree with RedTruck-VA, please post pics.

 

Haven't been able to take pics yet, but I looked again and it is an AC fan and the standard belt driven engine fan. So the only thing I can think is that when it's towing under heavy load, it "engages" the clutch harder and makes more noise as it spins faster to keep the motor cool...I guess haha. Like I said, it's super loud and only happens sometimes when towing. I'm pretty automotively inclined, but this is a new noise for me for sure.

 

Well as you know the cooling fan on the water pump is mechanical and not electrical so I dont know that it can adjust to engine load. You may want to keep an eye on things and trying to track it down a little more.