The present disclosure is directed to an auxiliary cleaning system for cleaning a gas turbine engine. The auxiliary cleaning system includes an external motoring source mechanically coupled to one or more engine shafts of the gas turbine engine. Thus, the external motoring source is configured to turn the one or more shafts. The auxiliary cleaning system also includes a cleaning apparatus configured to implement a cleaning procedure on the gas turbine engine while the external motoring source is turning the one or more shafts of the gas turbine engine.