iMac Clicking/Ticking/Popping sound coming from the back of the 27inch iMac

In the UK there are many Apple Stores so take it to another. First contact AppleCare (phone number is in your owners manual) and get a case ID. They will try to walk you through some trouble shooting steps which may or may not fix it. Because it's a random problem from the way you describe it these are very difficult to pinpoint.

Good luck,

Roger

Just got a brand new iMac and the same thing is happening. Order it on Black Friday and set it up December 1, 2010. The audio you included sounds EXACTLY like what I am hearing. As of right now I only hear it a handful of times a day. Has it gotten progressively worse over time for you?

I have thought about calling, but am not confident I'll get any real assistance from what I've read. I don't live anywhere near an Apple store so mine will either have to be shipped back or taken to a local repair place.

I agree with you... you'd think for the money that was paid we wouldn't have to deal with something like this. This is our third iMac and I've never had this problem before.

My new Imac (actually, already an exchange from AppleCare after repeated video card failures on previous Imac), from early december, started (10 days back) the very same ticking random noise you posted. When it comes on (an hour or two may elapse between ticking sequences), it's at 15 - 20 seconds intervals. It comes on at random but essentially now thru the entire day (originally just after 15 minutes from the morning boot and would disappear after 30 to 45 min. of use and now typically after every sleeping mode).
It does not appear to alter the functioning of the Imac although it is most irritating.
If returned to AppleCare or store, they may not hear it right a way unless they spend some time at it.
I'm hoping that, with time, it may disappear. If in the next few weeks/months it were to get worse (very distinguishable) and alter the functioning of the Imac, I suspect I would have an "easier" case to present to AppleCare.
How has it gone over time ? since your post goes back 2 - 3 months.