2007 dodge nitro leaks antifreeze when engine isnt running

The water pump creates suction on the coolant in the lower radiator hose while the engine is running. This could keep it from leaking, at least until pressure builds as the engine warms up. So take a good look at that lower hose while engine is off. Might just be a loose clamp but it may be rotting from the inside being eleven years old and exposed to a lot of heat and pressure.

It might even be the water pump.