If your air suspension is leaking down, you don't want to be under the coach, looking for the leak.
Always block the chassis frame to the ground before going under the coach.
Contact Spartan motor home support for an air system diagram linked to your chassis serial number.
1-800-543-4277
The diagram will give you an idea of where, and how, the front suspension system is isolated from the rear so you can safely start searching with a soapy water solution.