.............honestly i wouldn't think you should have any leak even without a cabin filter......might be something else wrong there, i will let others comment first tho b4 i say goto a dealership for maintenance. The link u provided is not the same as changing a cobalt/ion/G5/pursuit cabin filter, we don't have a write-up on here yet, maybe i should stop being lazy and make one........well i better do that before i post a link to another site lol i'll get in trouble probably, so hey check back in an hour I should have it posted up with pictures and "step by step" if u can call it that, it's pretty simple. i would ensure it is done every 10,000km-20,000km or for Americans every 6500miles-13000miles, mine was nasty dusty/black at 30,000km and wish i had done it much sooner. But ya check back in an hour i'll have a "How-To" posted for ya man. As for the water leak tho.......that doesn't sound good to me, i'm sure somebody else on here has a better idea what that is and will post it when they see this thread.
PS, they took your cabin air filter out and didn't replace it? Did you get charged for a new air filter? Did they ask you if you wanted it replaced? They should have put the one that was in there back in if you didn't ask them to replace it.
---------- Post added at 02:51 AM ---------- Previous post was at 01:12 AM ----------
My very first "how to" or DIY
http://www.chevycobaltforum.com/forum/showthread.php?t=2357