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I have a MacBook Air bought in early 2011. Lately it just can't seem to stay cool. With normal load, the CPU hovers between 80ºC and 100ºC, and if I use iStat / Fan Control to turn the fans up to full, completely idle my laptop will still only cool to 75ºC.

I've opened it up and taken a look, and there isn't an obscene amount of dust in there, though I did give it a good vacuum and dusted it with compressed air. In particular, the part of the heat sink where the fan blows through seemed a little clogged, but I took to it with a vacuum cleaner. This hasn't had any noticeable improvement.

I'm wondering if I need to look into the heatsink, since the fan seems to run correctly (there was some dust caked onto the fan blades, but nothing that stopped it spinning).

Here's a screenshot I took of iStat: Screenshot of iStat

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Obviously the cooling system on any computer needs to be free of dust and fluff for it to work effectively but you've checked that.

The next stage is to remove the radiator and heat-pipe assembly to check on the state of the thermal coupling between the CPU and heat-pipe. Clean off the old thermal paste and replace using a thin, even layer applied to the CPU. Apple have had a few issues over the years with hot-running CPUs caused by excessive thermal paste, so don't put too much on. The idea is simply to fill in imperfections between the CPU die and the heat-pipe that would otherwise be filled by air (air makes a better insulator than a conductor).

A cleaned and re-pasted cooler assembly should bring your temps back down again.

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