CPU fan buzzing/rattling in 27" (2009) imac

[pubjoe]

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?

 

[pubjoe]

One other thing. My plan was to plug the removed fan into a header on a PC motherboard so that I could isolate the noise to check if it IS the fan alone, but it seems that it has a very small non standard power connector. Does anyone have any suggestions on how I could power it (outside of the imac) so that I could do this check?

 

[pubjoe]

ok, I just dismantled, cleaned and re-oiled the bearing on the original fan and swapped it back into the imac, but it STILL rattles.

Please, any suggestions?

 

[cypress822]

I had a similar problem with a 2009 24 inch. Apple replaced all three fans....does yours have 3 fans too?

 

[pubjoe]

How much did that cost you, or was it done under warranty?

Yes there are three fans in the 27 inch. Two large fans on either side for the CPU and dvd drive/GPU and one small hdd fan in the middle. I'm certain the noise is coming from the CPU fan.

I don't mind the problem as I bought it second hand at a very cheap price so I got it 'as is'. It's no louder than some PCs I've had over the past. But I thought I'd be able to fix it. I thought either the CPU was running to hot and would need thermal paste re-applying or the fan is on the way out and I would swap it. Unfortunately, the temperatures are fine and the fan swap hasn't worked. And of course, now that I've failed to fix it, it's annoying me more.

Your right though, it's worth asking apple, it might be a cheap fix.

Although I do have a feeling that if I bought a new fan this time it would sort it. I think I just got unlucky with the replacement.