what is this and should it tick?

[felix da cat]

alright total newb question coming up.

far as i can tell this is some part of the vacuum system. its ticking quite loudly and im just not able to work out if it should?

any help would be awesome. thanks guys

http://i1225.photobucket.com/albums/...ara/photo2.jpg

[Treza360]

Been covered before. Activated charcoal filter.
http://www.vwwatercooled.org.au/f14/...ing-27365.html
Cheers,
Trent