99 Cobra, what cap is missing here?

[DarkRattle]

So I popped the hood and heard like something blowing out for a while and noticed a cap was missing off this "Thing" what cap is this and why did it come off?

http://i.imgur.com/3iIHs9d.png

 

[98 svt]

Can't see the pic

 

[DarkRattle]

Can't see the pic

Fixed, thanks for letting me know.

 

[98 svt]

Fixed, thanks for letting me know.

Still doesn't work lol

 

[DarkRattle]

Still doesn't work lol

Are you sure? It's literally a link to an imgur. Try refreshing the link a few times. Instead of clicking it, copy paste to URL

 

[omj]

That's an a/c port. The cap was probably not put back on the last time it was serviced.

 

[DarkRattle]

That's an a/c port. The cap was probably not put back on the last time it was serviced.

That's what I was thinking, thanks

 

[98 svt]

Copy/pasting the link did the trick.
As already mentioned, that's for your AC. It should ha e a black plastic cap on it.