Fan got really noisy

Question

My G4 has been always quite noisy since I got it like 5 years ago.A month ago I installed a second internal optical driver and also a USB 2.0 controller. The optical driver made a huge noise and shook the computer, so I took it out. The USB controller is working fine. The thing is, just after I did this installation, the computer´s fan got REALLY noisy. Much more than used to be. Since I work with audio, it does affect my work. I did try taking the USB controller out, but still noisy. When I turn on the computer, the fan is pretty quite, but after 1 or 2 minutes it starts to get noisier and noisier even though I am not using any software.
What could it cause that fan noise change?
Should I try replace the fan? witch model shoul I look for?
Thanks!
Damião.
PS:Sorry for English.

Answer 1

Hello Damião!
Could the dust make fan noisier
It can, but not always. If the fan has a thick but even coating of dirt, the extra weight can make the fan turn more slowly, and the noise is less than normal. On the other hand, an uneven coat of dirt could increase noise if it is enough to upset the balance of the fan.
If the fan is dirty, it is likely that other parts of the air passage system are also dirty. Reduced airflow means less effective cooling and the fans may run faster to overcome it.
Areas to check for blockage:
1) There is an air intake behind the four decorative ports on the lower front panel. If you place your hand palm-side up on the lower clear "handle" and curl your fingers, they will be in the intake. There is a perforated metal screen--make sure it is free of "dust bunnies."
2) there are two small but noisy fans in the front edge of the power supply. Clean them with a brush if needed but do not attempt to open the power supply unless you are a very experienced electronics tech.
3) The main fan--you've seen that this on is dirty. Check its grills for build-up also.
4) the back panel, especially internally where air is directed at it.
Computer position can also affect cooling. I attempt to leave at lease six inches (15cm) between the back of the case and any wall or upright desk unit to insure the exhaust air is properly dispersed. I also watch the clutter on my desk to keep any of it from getting behind the lower front handle where the primary air intake is located.
The USB card should not affect temperature and therefore fan noise unless the card required you to install software. In that case, the software running in teh background may be increasing the load on the processors. Most USB cards to not require software to work under Mac OSX.
PS: Sorry for English.
Your English is many times better than my Portuguese! You are doing very well.