Case Fans loud on cold boot

[diablo900t]

I've got 2 PCs I've built, and a strange thing I've noticed is after a while, when cold booting the machines, the case fans will run very loudly when the system boots, but will slow down around the time the OS has loaded (1-2 minutes).

I don't know if this has something to do with dust buildup, or just crappy fans, but it never happened (with both machines) when I first put them together, only a couple of months after they had been running. Again these are the junk case fans, no temperature contro, etc.

Any thoughts?

EDIT:

I should mention they are both in a cool and dry room.

 

[Fullmetal Chocobo]

Because your motherboard probably has software to control the speed of the fans, and thus doesn't load until the OS does. What are these fans connected to, and how are they connected?

 

[diablo900t]

The fans are just connected directly to the power supply, they aren't connected to the motherboard at all. The system is usually at a fairly low temp when it first turns on, so I dont' know if this has anything to do with it, the room itself is usually <70 degrees at all times.

 

[tiap]

This is very common with cheap sleeve bearing fans. You are hearing the friction created. The bearings are simply worn/dried out. It happens more in cooler weather. Spend the extra couple of bucks and get double ball bearing fans. Always better, no matter what make.

 

[diablo900t]

Originally posted by: tiap
This is very common with cheap sleeve bearing fans. You are hearing the friction created. The bearings are simply worn/dried out. It happens more in cooler weather. Spend the extra couple of bucks and get double ball bearing fans. Always better, no matter what make.

I think you hit the nail right on the head. It sounds like the fans are rubbing when they start up. Its only the crappy fans that come with this case where this occurs so it certainly makes sense. Thanks for the info.