Windows 7 - Fan Started Running loudly lately

The other day I got home and I heard this screech. I followed the noise to my computer. I've had this computer for about a year and a half and I've never had this problem before. I shut it down, opened the case and used canned air to clean the fans. Then i rebooted and the noise was gone. Tonight out of nowhere, the fan started screeching again. I checked the cpu temp on the thermometer on the case of the computer and cpu temp was normal at 32 degrees C. I turned the computer so it had more air and blew in it and the fan stopped making noise. I Dled CPUID Hardware Monitor and it looks like all the temps are fine. The fans are running at 1339 - 1383 respectively. I have liquid cooling and a couple of fans and if it's not the CPU that's running hot, what else might it be? Please advise, thanks

Bell,

Without hurting yourself, try and temporarily stop all fans that are running in the computer one at a time. Perhaps gently press on the middle part of the fan so that the blades don't hit you, and you can find out if it is screeching, pressing harder and harder until it stops. There are many fans, side fans, high fans, low fans. test em all. If you find the bad one, look up ways you might be able to fix it, or just replace it. Fans can go bad. Dust and lack of greese may be what is causing the screeches. If it isn't a fan, it could be the hard drive, but we'll get to that after you post back. Good luck! (Please be careful)

Be sure to check your graphics card fan (if you have one) as that's a common source of squeeling

If your fans have bearings this will be the cause. if the bearings don't have enough grease they can pit (a spot wears or rusts out) if enough pitting occurs the fan can cease up or in your case start squealing. it is very rare that CPU fans are ball bearing because of the heat they have to deal with and the fact that they need grease (obviously grease and heat don't mix). if a fan has pitted bearings it is a throw away job.
hope this helps...

It doesn't permanently screech, so I can't tell which fan it is until it happens again - and I hope it won't happen again. I went again today to clean all the fans and the one on the power supply and the one connected to the CPU is almost impossible to get to. It's hard to tell what's going on in there much less get the dust off it. If the fan that was screeching was doing so because something got too hot suddenly, then maybe it wasn't the fan having a problem. I'm not sure how to troubleshoot this at this time. Thanks

You might consider leaving your case open. If things are getting hot, without actually touching anything hot and being very careful, put your hand over fan areas such as the graphics card, around the case, and also in the case and over the motherboard areas. You will be able to feel hot. To acurately test it, you will need software that mesures the temp, such as coretemp and speedfan.

To get dust off, buy a compressed air canister to blow out the dust. Things never get hot suddenly, but do more so within games and heavy duty applications. As I said, try temporarily leaving the case open to quickly get to the problem, if possible. Make sure the computer doesn't overheat though, because airflow will be disrupted.

Can also temporarily disable non-critical fans to see if the problem continues with the particular fan, but this will take a long time as you've said it doesn't happen often. One or two disabled case fans shouldn't hurt temporarily, but be vigilant and careful. CPU and GPU fans are critical fans, don't disable them.