Help on Chimney Repair

[Smatz]

Hello,
Upon cleaning out a wasps nest around the stuccoed wooden surround around my gas fireplace chimney, I noticed the end cap on the 4" chimney piping was corroded off. Later on I also found the larger piece that covers the overall housing buried in the dirt of that space as well. I found the larger piece after putting on a new end cap with high temp caulking. Now that the end cap is attached to the 4" chimney pipe, the larger housing assembly will not attach to the larger chimney housing because the end cap sticks down too far.
The 4" pipe seems to be somewhat loose in the housing as well, be that I mean it can be moved back and forth.
My question is: does the larger housing need to be on the chimney assembly or is it ok with just the 4" end cap? The gas fireplace is in the basement so I assume this end cap part of the chimney is the bottom side of a T.

 

[Smooky]

A proper cap is designed to allow exhaust gases to escape and prevent rain water from getting into the pipe. It looks like you sealed up the exhaust pipe so the exhaust fumes will not escape. Rain water may get into the annular space and leak into your basement. I think you need a special vent cap for double wall stove pipe. Be careful so you don’t asphyxiate yourself. Ask the gas company etc.

http://www.woodlanddirect.com/8-inc..._a_7c2594455&gclid=CIHSm5mmz8gCFdiRHwodQSsIzw