The phantom valve tap of the 4.0 is well documented. Mine does it warm, cold or otherwise. If it's running, it's tapping. Always has, always will. Could it just be the metal expanding? How loud is this ticking?
The water could simply be the moisture from your exhaust pipe. I see cars on cold mornings with water trickling out the tail pipes. I know that rusted exhausts are often the result of a lot of short trips, as the exhaust doesn't get or stay hot enough to vaporize it all, and it just sits in there. To be sure though, after you pull out, stop and check out what's on the ground. Touch and smell it. If it's just water, you're fine. If it's got antifreeze, you may have a problem. If it's oil, well, duh, and if it's petrol, get that checked out right away. My neighbor has a Grand Cherokee that sits for weeks on end. The squirrels chewed the fuel line. His wife took it to work one day and wound up needing a tow. Fuel leaks can be hazardous to your and your jeeps well being.