I have a 2007 Mini S, and for a while now, my car makes a high pitch chirping noise when I start the car, and it continues to make noise as I drive, at various intervals dependent on my speed. It seems to happen on a cold startup, is this a serious issue that I should take a look at? What is causing it?

 

others have said this was a bad breather valve in the valve cover.

 

Serpentine Belt ?

 

My chirping noise was the serpentine belt pulley losing its rubber cover, afterwards it was metal on metal and made the noise louder and all the time.