brutherb-
Your coach has a backup brake system. It uses an electric pump. If the engine stops running you can press on the brake pedal and it should activate the backup brake system.
It will make noise under two conditions:
1) With the engine off, you press the brake pedal, or
2) With the ignition switch in the accessory position, without pressing the brake pedal
Search the owner's manual (link
here) for "Hydroboost" or "Hydromax."