Hi!
Are you sure it's the fan..? It's possible that your drive is making a lot of noise.
What I do to test, is to unplug the fan, put in a disc and so you know for sure if it's the fan or not.
If it's the fan, then replace it for a new one and see how that goes.
If the drive is making a lot of noise, then check the disc rotate motor AND the white piece on top of the disc drive. One of those can make a lot of (grinding) noise.