When the car is cold it has an annoying rattle that comes from underneath the car, could this be the exhaust rattling because it is disconnected or something more serious like the turbo slipping and hitting? It almost sounds like a fan hitting or the timing belt slipping, but the belt has recently been replaced. The real question is should this be something to worry about?

 

Most common rattle is probably the cat converter shield.

I'd say that any rattle is a bad thing if you don't know what it is. I'd be concerned.

But since we can't see your car, and can't hear the rattle, there is really no way for anyone to KNOW what the rattle really is.

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