I had similar issues with mine.
The top cap will screw off and make cleaning it easier. Take the battery out first and it will take pressure off the center post.
There is a silicone rubber gasket that seals the top post and liquids from the internal electronics.
Are you over filling the cartomizers? Are you using a
tank and it is flooding the coil?
These are some of the possible causes for the leakage issue you are having.
Steve