Does anybody have an idea about why I'm hearing my radiator fan now almost all the time? Upon further investigation today, I popped the hood and listened to it at idle. It appears to not know whether to run or not. It starts to really turn, then backs off a bit, then goes faster, then slower. It's cold here (about 35) so I know the engine doesn't need the extra cooling. Is there a sensor for this fan that could have been messed up when they did the body lift? That's when I started noticing it (immediately). It's going back to the shop, but I'd like to know what I'm talking about when I go. Anybody?

 

Need more info. What kind of vehicle, is the fan electric or clutch driven?

 

Clutch driven. I had a lift done recently and there is a 3" gap where they lowered the radiator shroud. Could that be making a difference? It never made the noise before. It's worse when it's cold. When I start up in the morning, it sounds normal for about 5 seconds. Then the fan kicks in and mimics the engine rpm's. As the truck warms up, it gets a little better, but never goes away.

 

I've been asking around the forum about this and may have something to add that may influence things. I have a fan howl/roar that comes on about 10 seconds after I start my 2001 Supercrew with a 5.4 L. It's really bad when it's cold, but I hear it all the time. The rpm's of the sound go up somewhat to a point, then don't go any higher. I don't think it ever stops. It does sound after its warmed up like it can't make up it's mind whether to run or not at idle. The more I listen to it, the more it sounds like an electric fan. I didn't buy the truck new, so I don't know if the fan is the OEM centrifigal clutch or an electric one, although it came from the Phoenix area (read HOT). It looks like stock (single fan). Haven't even thought to see if it's hooked up to the front of the engine or at the radiator. The more I type, the more ideas I think of. I'm guessing that the stock fans are hooked up to the motor and the electric ones are at the radiator. Does that sound correct? I had a 3" body lift done, and that is when I started hearing the noise. They have had it back 3 times, but can't find anything wrong. They suggested I take it to the dealer.

 

it is absolutely hooked to the front of the engine and run by the belt.

if it is not roaring really loudly and your performance is normal than there is nothing wrong. these fans do all sorts of weird stuff/sounds depending on the weather, humidity, etc.