Last night I cranked my truck to let it warm up for a few minutes before driving and noticed a noise coming from under the hood that sounded like a fan going bad. Could my mechanical fan be going out? Is there any way to check the mechanical fan? Thanks for any help.

 

You should be able to spin the fan by hand with the engine OFF, and cool. If that is find it is probably the tensioner pulley or idler pulley bearings going bad.