My 2003 diamante makes an awful noise when started cold. It sounds like belt/pulley chatter that lasts the first few seconds to as much as 30 seconds then goes away. My mechanic has inspected and replaced the belt and tensioner with no improvement. Anyone have any ideas??

 

"Valve tap at start-up is common on DOHC models and usually goes away after a couple minutes, but replacement hydraulic valve adjusters are required if noise persists"

I remember reading about that somewhere, hope that helps, I know its not the belt/pulley but worth a shot