I have been getting two odd noises from my engine lately. The first is when you start the car up i get a rattle like the timing chain is rattling. It lasts for about 30 sec or so and then goes away. The second is a fluttering type noise that sounds like its coming from the supercharger. It only happens when im accel and the supercharger is putting out boost. if anyone have any ideas it would be a big help.

 

lifter noise perhaps. or cold blower

flutter = bypass valve.

it's fine

 

I've seen/heard this happen. What octane gas do you use? Try putting a reputable source of gas in it ... the extra few cents will help!

 

I've been getting the exact same then when it starts sounds terrible but like you said it always goes away after about 30 seconds.

 

the rattle is the tensioner, i had this apparently it is a hydrolic tensioner and when pressure builds up it should go away

mine made the all the time, apparently my tensioner was bad, and fixed under warrenty

 

the rattle could also be the throw-out bearing. Does it go away when you dis-engage the clutch? I know my throw-out bearing rattles a bit when it is cold outside, but it goes away after a few minutes after start up....i don't have a cobalt though, but it could be alot of things. Pop the hood next time you start up and try to identify exactly where it is coming from. The flutter is probably your bpv.

 

I hear a rattle too, sounds like it could be my exterior belt tensioner. When It's cold i place my ear right on the yop by valve cover, and i couldnt hear anything. but it's definetly something exterior. It goes, and comes as it pleases...
WEIRD