My late 2011 MacBook Pro has been incredibly noisy lately. It was only quiet when it was really idle or had just started up, but as soon as it heated up a bit, the fans would blow at full speed and fail to cool the Mac. I figured dust buildup could be the problem.
Before I even ordered the parts, I'd already checked the iFixit guides for right and left fan replacement. I opened up the mac, cleaned out some dust, and noticed the fan blades looked really hairy. My diagnosis was that the blades were too dusty to move any air, leading the mac to spin them up to max speed in a futile attempt to move more air (this diagnosis may have been wrong: see later).
In the distant past, I'd tried to clean dirty fan blades before, and that got incredibly messy, so I preferred to just replace the fans. I first checked with Apple and official repair shops, and it would mean I'd have to miss my MacBook for a couple of days. Not acceptable for such a simple repair, so I ordered the parts on iFixit, and did it myself.
The repair was fairly trivial. Opening up the Macbook is really easy. I had to search a bit to figure out where to unhook the battery, but that wasn't hard either. Using the spudger and a careful hand, unhooking the plugs for the fans wasn't very hard either.
After unscrewing and removing the fans, I noticed that the dust on the fan blades was mostly on the edges. The fans looked like they should still be usable. But there was a thick layer of dust between the fan and the exhaust. That was very likely what blocked the airflow. If I'd just removed that, I might not even have needed the new fans (though I'm still glad I've got clean fans now).
I was impressed with the design of the Macbook that made the dust build up primarily at the most harmless part of the macbook. The rest of the insides had very little dust, which is a different experience from what I've seen in PCs with cooling fans on the CPU.
Cleaning the dust was fairly easy. I remembered I had a small USB-powered vaccuum cleaner, which helped me a lot to remove dust from hard-to-reach places.
Putting the new fans in was also easy. The hardest part of the whole repair was actually putting the screws into bottom cover of the Macbook. Some of the screw holes are at a slight angle, which makes it really hard to get the screw in just right. Often after a few turns, it gets stuck, and I have to try again. I had no such problems with any of the screws on the inside.
Another problem: the weather was very hot, and I was sweating like crazy. At some point, a drop of sweat fell on the motherboard. Fortunately the battery wasn't connected, and it was quickly cleaned up, but this does show why it's so important to unhook the battery first. And maybe a sweat band would have been a good idea.
But the repair was a success. My fans are spinning quietly again. The jet engine noise is completely gone.
If your fans are dusty, maybe you don't need new fans at all. The real dust buildup is just beyond the fans. Use the guide to get the fans out, remove the dust, and put the old fans back in. It's an easy repair, as long as you're careful around the motherboard.
Speaking of careful around the motherboard: be careful with sweat when it's hot. A sweat band is a cheap investment and might save you some stress here. And of course do not skip unhooking the battery. That is just vital.
I was really glad to discover iFixit's fans are the exact same brand as the official ones from Apple. Apple refuses to sell theirs separately, and all their official support shops aren't allowed to either, so I was afraid iFixit's fans would be cheap knockoffs. They're not. They're the real deal, which gives me great confidence in my new fans.