James, you forced me in to opening the hood and looking. Yes it disappears into the front but I sure can't follow it without pulling the radiator(?). mine is new and came from the dealer. One end goes to the top of the thermostat and the other end goes into the top of the overflow tank. I'll look in my AllData subscription and see if I can get more info.
Anziani
The only thing I could find on ALLDATA was reference to a "air" line that has a cap on it and terminates next to the windshield washer bottle. Apparently one removes the cap from this hose when removing the expansion tank. Yes, I'm just as confused as you probably are.