'81 FC air leak

[doug_ngl]

Howdy Crew,
Well, I got the Bird moved into its garage for the winter and when I
parked it, there was a sizeable air leak (noise) coming from the front
end. Upon investagation, I found the leak coming from whats looks like
a small vaccum solenoid that appears to be on the end of an air
manifold. It is on the drivers side, pretty much inside and just above
the step hole in the bumper. I think the manifold distributes air to
the suspension. The air is leaking out of a small (1/8") tube coming
out of the bottom of this gizmo. Any ideas? It's cold here and I
suppose an ice crystal could be in there, but what is this thing, what
does it do, why is it leaking air? What is the meaning of life. Any
and all input is appreciated. Doug Engel, Gunison,CO 1981 FC35SB