Need help re-attaching mysterious coolant pipe -> 90 GP 3

[bringerofwar]

Hi, I was messing around with the coolant resivoir tank, and when i went to re-attach it, i noticed that one of the hoses from it was not connected to anything.

I know the one hose from the bottom of the tank goes into the rap cap assembly at the top of the rad, and this other hose comes from the top cap in the resivoir. Is this hose just an overflow hose, or does it connect to the rest of the coolant system?

Any input is welcome, as i need this car for tomorrow morning

Thanks

1990 Pontiac Grand Prix
3.1L V6