Hi, Help would be greatly appreciated. Today i replaced my 2009 27" imac's CPU fan in an attempt to fix the high pitched rattle coming from that area. I bought the fan from ebay and installed it but unfortunately I am still getting the same sound. The temperatures are fine and the fan speed is 940rpm when idling. I'm pretty sure it's the fan creating the sound as it is most audible from that exact spot and I can direct the noise towards me by cupping my hand under the air intake area at the lower left of the imac - which makes a dramatic difference in volume. The imac is over 3 years old and I guess the replacement fan was too. So it's possible that they have the same problem (worn bearings). But before I go to too much trouble, can anyone tell me if perhaps there is a common physical problem which may be causing this high pitched rattling? It seems strange that the noise is just the same with both fans, when I have a 2006 and a 2007 imac both running nice and quietly. Or, if it is still the new fan's bearings causing the noise, does anyone have any experience in cleaning and re-greasing the bearings of an old fan?