My cooler sounds bad sometimes. No much loud. Sounds like four-five hair fibers torure it with slaping on its propellers (up to +12dB). I don't hear sound all time and there is no rule in its appearing.

I done some cleanings with art brushes but only what came out was LOT of burned smut.

What to do?

replace

ok wait. You cleaned your fan with an art brush? lol, thats not going to get is very clean, you need a can of compressed air. From the sound of it its probably bad so just get a new one, they are cheap. (I am assuming your talking about a computer fan or CPU fan)

Is it not some wire's from other parts of the computer hitting the fan some how?

Usually if it's making alot of noises, the ball bearing's getting wore out or whatever. Easiest thing really is to get a new one.

Most CPU coolers have an 80mm fan on them (unless I'm smoking crack). IF the cooler itself is expensive, replace just the fan. Fans are typically cheap as hell, it's the huge copper coolers that cost $$$.