Laptop Fan Noise w/o visible problem


Oct 28, 2015
Hello there,
I have an old Dell Precision M4500 which works great except that the fan has started to rattle.
Now i removed the fan from the cooler unit and to my eyes it doesn't seem like there is a problem with the fan, it doesn't make any sound by itself when I spin it. Now when i put it back into the cooling unit and spin it it, now I can hear it rattling. I can't see a visible problem. What am I missing, what is creating the noise?

Sincerely Val