noise - Rattling laptop fan after applying compressed air
2014-07
Steven Liekens
I recently used a can of compressed air to clear my laptop's air vents from dust and other dirt that accumulated over time. While doing so, I did not hold the CPU fan in place in order to stop it from spinning as a result of the inwards air flow.
Now, when the machine is powered on, I can clearly hear a rattling noise coming from the CPU fan. There is no noticeable increase in CPU temperature as far as I can tell. Besides the noise, it seems to work perfectly fine even under heavy load.
I'm interested in the technical explanation for what is happening and why it is happening. Also, is this a problem that can/should be fixed without getting a replacement fan?
EDIT
The noise is actually most noticeable when the machine is idling (i.e. when the fan is spinning at a moderate speed). As the fan speeds up under heavy CPU load, the rattling noise does not really increase in loudness, only in frequency and tone. I haven't had the chance to open it up yet, so all ideas are still welcome.
EDIT
I finally got around to taking a closer look, this is what I found: 
It looked pretty bad, but the problem still persists after thoroughly cleaning the fan. Any other ideas? I'm about to order a replacement fan.
music2myear
If you didn't hold the blades, as you note, you may have overspooled the fan, causing it to spin much faster and deal with forces much stronger than it was designed for.
Blowing sustained blasts directly into a laptop vent is never a good idea. Short blasts obliquely are OK, but it's usually best to control the fan spin by holding the blade with some implement.
Now that the fan is probably damaged, besides checking for obvious stuff like Carl B suggests, you'll have to replace the fan.
Carl B
As you have blown into the vent, the one issue that comes to mind is that there is a blade or two with a little schmoots (dirt/dust) on it causing an imbalance. Now as the fan spins, the imbalance will give a rattling sound.
The other is that there is a clump of dust, hair or whatever around the fan shroud that the fan tips are hitting as they spin.
As you note the fan still spins and no temp problems are noticed even under load, it would seem that a loaded blade or two may be the problem.
You would want to open up the laptop to really see what is what and you will probably notice that the dust that was in the vent, in now spread around inside.
Some laptop fans have easy access to the blades and you can use a q-tip to wipe them down one by one. Not sure if yours is like this or if the shroud around the fan can be removed, but it would be a good first, cheap step to try. I would also, get some more air and when the laptop is open, give it another good blast.
DO NOT be tempted to use a vacuum cleaner. That could cause static/static discharge causing potential problems.
Caffeine Coma
My Quad-Core Mac Pro tower is two days old. Initially, I was impressed with how quiet it was compared to my older Macbook Pro. Then on day two, for some reason it started running very loudly. It's not just a "little" loud- my wife walked into the room and asked what the noise was.
At first I thought this was just because I was hitting the CPU a bit (importing my iPhone library into iLife '09, and running Eclipse). But now that that's done, Activity Monitor shows a virtually idle CPU; there's nothing running that ought to be causing this, as far as I can tell.
I tried powering it off & letting it cool down for a few minutes to no avail; about 10 seconds after powering up, the box gets loud again. I took a look at it with the side cover off, and it seems to be the fan near the top middle, between the power supply and the disk drive.
It can't be a dust issue, as the machine is only 2 days old (and I peeked inside anyway just to be sure- clean). I did do a software update over the past 24 hours or so, but I can't say that it occurred immediately after that. I also did a migration of my old apps and data from my MBPro, for what it's worth.
- Why is it suddenly so loud?
- How can I monitor the fan speed and various system temperatures?
My temps and fan speeds:
UPDATE 1:
Took it to the Apple Store. They took it in the back (where it's presumably quieter) and ran a fan diagnostic; no problems were found. The guy also told me that it was "a little loud", but normal. I don't buy it. It was virtually silent the first 24 hours I was using it. They would not replace/service it in the store (grrr... that's why I went there, as directed by Apple Care) but said I could get a replacement from the online store, as it was just purchased. I think I will try that.
UPDATE 2:
Apple is letting me send it back for a replacement. Glad to see so many responses to this question mentioning that the MacPros are usually silent; it's not all just in my head.
emgee
I would image the drive and take it back. Sounds like a problem in the fan control hardware and/or firmware. I have a few MacPros at work and they are quiet. The hardware test you're already doing is also a good idea.
ridogi
Is there enough space behind it for air flow?
Is the case closed when it is powered on (it should be)?
Have you viewed "All Processes" and not just "My Processes" in activity monitor to make sure a processor isn't pegged?
Have you run Software Update to make sure you have the latest OS?
Have you run the Apple Hardware Test?
Jon Hadley
It might be that the fan (or a bearing inside it) is broken, causing the extra noise?
Or perhaps the temperature sensor is faulty and things the CPU is much hotter than it actually is?
EDIT: Also, I've heard of faulty power supplies overheating the battery and laptop, might be worth checking too.