I did a quick look over under the hood of my '07 and saw that my coolant overflow tank was low, still a good amount in there, just barely below the MIN line. No big deal I grabbed my jug of coolant to top it off and as soon as I started taking the cap off it hissed out the pressure and brought the coolant right back up the the FULL line. What's goin' on here? Is this anything to worry about? By the way the truck was COLD, no warmth from anywhere under the hood, as was the coolant when I stuck my finger in.

 

All of our service trucks do the same thing, and they are '04 to '07. Do you have the sticker on your tank, or just the molded lines?

 

Pretty sure it's a sticker

 

From what I have seen on ours, the sticker makes the low/full marks lower then the molded levels.

 

On the bottle, the "Low" mark is the new "high" mark according to Ford TSB's The sticker just shows this. All coolant systems are pressurized. It raises the boiling point of the coolant to have it pressurize. When it starts getting over-pressurized, that's when you need to worry.