what is that air line for?

It controls the way air blows out of vents, floor def. if you move lever to a different poss. it should stop leaking at good one, then find the one its leaking from small rubber air pod that controls flap to turn air from one to another flap door?

 

Underneath the radio behind the trash can the air manifold. The sensors and for the cruise control, parking break and sevwral othera. The parking break or cruise control usually go bad. They are cheep but you need a a special socket to remove and replace

 

Yup I would say the air manifold also is what you are seeing. My manifold went bad on me when I was replacing one of the switches. I tried loosening the switch that was leaking and the metal insert started spinning. If I were you I would buy a replacement and have it available just in case. It could be enough to ground you on the side of the road if you were to have a leak.

 

Each switch controls something different. There is like 4 or 5 different designs of the manifold. It really all depends, do you have a switch leaking or is the manifold itself leaking? If the manifold is leaking I would recommend replacing it (cheap $125), I wouldn't recommend trying to doctor it up. If you have a switch leaking well that is a cheap easy fix. If you have to replace the manifold I would recommend getting some paint pens from the "arts and crafts" department at your local supermarket and color code everything so it makes installation that much easier. Good luck

 

It replaced my air manifold and had a hell of a time getting the new lines to not leak.
Had to eventually take it to a mechanic. The air lines have to be perfectly straight or they will leak. I'm afraid when I have to go into the dash to repair something and just bump any air line and creating a new leak.