Hector is being too modest. Nobody knows the suspension system as well as he does.

I do want to make one thing clear. The leakdown of the suspension system is not the problem, but is a symptom of the problem. When the aux air drops, it in turn causes the suspension to exhaust air as Hector has described.

If you cannot hear the leak here is a tip that may help isolate it.

Your Liberty has a manifold in the lower steer compartment. All of the house systems are supplied aux air from that manifold which may have as many as 6 air lines coming from it. I would suggest you disconnect and plug the air supply to the mainfold to see if the bus holds aux pressure. (you can check pressure with a tire gauge at the valve located on the rear bulkhead of that compartment.

If the aux air holds the leak is in the house side and by removing and plugging the mainfold at each air line you will find which circuit is the leak.

If the aux air pressure drops with the aux air to the manifold plugged, focus on the bus. That could be the door air lock, the belt tensioners, leaks at the solenoids that control the suspension, etc.

My guess is like the rest of us, unless and until you chase them down you probably have numerous small leaks that have occurred over time and were neglected.