Help was a foreman 500 fan squeak

Hi,

I was riding my 2005 foreman 500s and when the engine got warm, the fan tried to go on, but all I got was a "terrible squeaking sound" and the fan did not go on. I then turned off the atv and checked the fan. The fan spun freely by hand and was relatively clean. I let the machine cool down for 10 minutes and when I restarted the machine the squeak was gone since the machine had cooled down. The fan made this squeaking 3-4 more times on the was back to the truck. Each time this "squeak" occured I instantly turned off the machine and waited at least 10 minutes as I was afraid of potential engine damage since the fan would not turn on. Any thoughts on why my fan will not turn on/squeak?

thanks