Methods and systems for in situ cleaning of internal cooling circuits of a turbine engine with detergent that provide cleaning a turbine engine that includes circumferentially arranged internal impingement cooling circuits that each include a baffle plate configured to air cool a respective surface or component of the turbine engine. Detergent is introduced through the outer wall and proximate to a back side of a baffle plate such that the detergent passes through at least one aperture in the baffle plate and acts at least upon the surface or component that the baffle plate is configured to cool. The detergent may also act on the front side of the baffle plate that is proximate to the surface or component.