Well I have a grinding noise on the inside of my Mac Pro somewhere. I thought it was the forward most chassis fan. It turned out to be the fan that is built-in to the heat sink of the CPU.
So when the Apple Store replaced the fan I originally asked them to replace the machine came back scratched. It is not that bad and more of an annoyance then anything. I'm so neurotic about keeping my toys meticulous. 🙂 Sometimes I think it gets in the way of enjoying them... anyways 🙄
I am not really mad at the tech's at the Apple Store either, I spend so much money there for business they basically take care of any problems I have with no questions. 🙂