When to change coolant ? I have 45k on my 04 GT and coolant has never been changed.

 

Never hurts to do a coolant flush. I would say with that amount of millage it would be fair to flush it

 

Yikes! Do it yesterday! 4 cents - Flush and replace coolant every 2 years minimum (including the overflow tank), esp. since there's a bunch of aluminum components in the cooling system. Throw in some "No-rosion"-type product in there for good measure. Don't use tap/hard water whenever possible. "Burp" the air out of the system during refilling.