MacBook Pro intermittently emitting strange noise

Question

Starting a few days ago my MacBook Pro (late 2008, aluminium) has started occasionally emitting a strange noise. It happens maybe a couple times a day and lasts for maybe a couple minutes at a time. The computer has been working fine until now. I've not noticed any other issues besides the noise. Not sure if it's the hard drive or the fan but this obviously sounds rather concerning.

I would describe the sound as a sort of buzzing or grinding noise, which occurs either in bursts or occasionally continuously for several seconds at a time. Here's an audio sample: https://dl.dropboxusercontent.com/u/4563526/mbp-noise.m4a

What is causing this issue and what can I do about it?

Solution

There are three things that come to mind:

Hard Disk: Run a disk check, but I don't think this is it, I doubt any OS would boot off a disk making that noise, but since it is the worst of the possible scenarios I would check it first

Fan: If a fan is stuck, bent or has a lot of dust stuck in it it might make that noise. Try using something like Temperature Monitor to check on fan speeds and any unusual temperature increases.

CD/DVD Drive: Another moving part that might be produce such noises in case of stuck/broken parts. The least worrisome problem - try disabling the drive and see if you still get the noises.

If you feel comfortable with it you can take the back off and check for problems your self, if not you could use a can of compressed air to spray in the vents at the back and in the CD drive in an attempt to clear out possible debris.

Also as with any computer problem, I would recommend you have a updated backup of your data before you attempt any repairs.

Comments

[Jake Petroules]

The noise seems to be the fan(s) or at least the right-side fan. If I spin the left-side fan with my finger it will spin for a couple of seconds in complete silence and then come to a stop, however the right fan stops spinning immediately after I release my finger, while making a grinding/buzzing noise. I suppose the right-side fan might be misaligned somehow but it looked fine and didn't feel loose, crooked or stiff nor did there seem to be any debris. Noise was consistent with fan speed changes observed with smcFanControl.

[Jake Petroules]

It seems that during the shorter bursts of grinding noises heard in the audio sample above, the fan was jumping between 0 and 200 rpm; almost as if it was trying to get started but failing to do so. Both fan usually goes back to around a 2000 rpm average after these occasionally bouts of noise. So, I'm not sure why the fan is making this noise but it's definitely the fan.

[peanut_butter]

There are a lot of things that can go wrong with a fan, and few of them have a simple fix. I would recommend replacing it, either yourself or get a pro.

[Jake Petroules]

This machine might be replaced soon so I'm not overly concerned but is an issue like this with the fan likely to damage the machine in any way other than potential overheating?

[peanut_butter]

I can't think of any other way.