Engine/Transmission (1994 - 1998) Question on the fan

[AMink]

I know that when my engine gets hot, the fan comes on. I can hear that. However, when I start my truck, the fan turns too. What is the difference? I know that the dealer used to (maybe still does) sell a different fan clutch that keeps the fan from turning until the engine is too hot. Is that a worthwhile purchase? So many questions, so little money! Especially now that fuel is $3!

 

[DBraunig]

an instructor once told me that the fan comes on when cold to pull any moisture or condensation out of the radiator/condenser to dry it out. otherwise it would slowly heat up and steam, making it look like a problem that really isn't there. I dont know if thats true or not, but it made sense after i thought about it, Dave.

 

[vssman]

The fan uses a viscous coupling as the clutching mechanism. As a result it turns at a certain RPM that is "designed" into the clutch to allow for proper air flow across the A/C condensor and intercooler. Removing it or upgrading to a Horton (which isn't available anymore) really won't give you a noticeable difference in MPG - at least I didn't see one when I removed mine a few winters ago. I now run straight electrics and haven't seen any difference in MPG, just faster warm ups for the 'chilly' months... By the way, without any air flow from a fan you can see steam rising from the nose given the correct conditions.

 

[AMink]

So when the "jet engine" sound starts, it goes from viscous to a full lockup?

 

[LandShark]

So when the "jet engine" sound starts, it goes from viscous to a full lockup?

Yea, that's the sound it makes. I hadn't heard mine for two years until this last week when I was pulling a 7,000 pound boat and trailer up a steep grade for about 1 mile and I couldn't make it out of second gear.