Why is my clutch fan pushing so much air when motor is cold/?
 

hey guys, when I first start the truck and drive for the first 2 miles the clutch fan is loud as hell. loud meaning the cfm is very high. Is this normal?? I would think it would be low cfm at first so motor can get warm?? There is no abnormal noise coming from it and after 3 miles it gets quiet.

:icon_shrug:

Its normal,at least on the 2 1st gens i had...the fans sound like hurricanes under the hood until they warm up.

Could be that the previous owner installed a heavy duty fan clutch or it could be the clutch starting to go. A standard duty clutch should free wheel for the most part on cold starts. You should be able to spin it by hand and make 1 or more revolutions of the fan before it will stop. It shouldn't cause any real problems though, but if you wanted it gone, a new clutch would fix it.

Thanks for the reply guys. My parents are the orig owners of my 1995 s10 and it is unmolested. I remember my father bitching to me 5 years ago about the noise and insisted it never did it when it was new. he brought it to the dealer back then and they supposedly changed the clutch fan but the noise was still there. I have been working on cars for about 10 years now but amazingly never owned a car with a clutch fan before so I dont know whats normal. I am going to spin the blades and see the resistance.

thanks!!

swartlkk, I checked it out today. it is quite stiff when i try to spin it by hand. when i try to spin it , it will spin about 2 inchs, thats it. no way in hell it will spin a full rotation. does this mean it is bad??

thanks man!

Sounds normal to me. When the engine is shut down after reaching normal operating temperature, the silicone fluid within the clutch transfers from one chamber to another. It usually takes approximately 2-4 hours for this to happen. When the engine is re-started, the fan spins at approximately 80% to 90% of water pump RPM causing it to “roar”. As the silicone fluid is redistributed evenly within the clutch, it gradually disengages and the fan begins to free wheel causing the "roar" to decrease. The fan will continue to free wheel until the air temperature at the thermostatic coil on the clutch reaches approximately 150F. Internal components of the clutch gradually redistribute the silicone fluid and begin to engage the clutch. As the clutch engages, airflow is increased across the radiator allowing it to dissipate more heat. When airflow temperature across the coil reaches approximately 195F, the clutch becomes fully engaged and the “roar” becomes noticeable again. When the air temperature at the coil decreases, the clutch starts to disengage, and the cycle starts over. Think of the fan clutch as a “temperature regulator” or “thermostat” for the radiator.

Is it possible the fan would make a rattle sort of noise instead of roaring? My wife's Blazer did this upon startup, but after I drove it a couple of miles, it stopped. And wouldn't do it again, even when starting up, leading me to think that it has something to do with the engine reaching operating temp.

Never heard one do that before, but I suppose it's possible. Usually they either lock up completely, making it roar all the time, or free wheel and never roar. I have heard serpentine belt tensioners and pulleys make a rattle sound that goes away after warm up.