The most common cause of leakage from the Kanger Evod is a worn-out coil, so try changing that first!
Another common reason is a blockage in the airflow - around the base of the tank (the silver ring) you'll see 3 very small holes which are essential for allowing air to pass through. Check that these are clean and clear of dust/dirt by pushing a pin or similar object through each hole.
If you're still having issues, your Evod may have a crack somewhere - they're robust but not indestructible, and sometimes even a hairline crack can cause leakage. If that's the case, it's simply time for a new one!