What happened
On July 12, 2015, an Airbus A320-214 arrived at Katowice/Pyrzowice Airport (EPKT) where maintenance personnel from organization A identified a hydraulic fluid leak in the green hydraulic system. The leak was located on a manifold body and was determined to be outside of allowable limits. Initial attempts to rectify the issue by replacing seals on the fittings and valve failed to stop the leak. Consequently, the manifold, fittings, and valve were replaced; however, the leak persisted.
Maintenance personnel from organization B were subsequently called to assist. Their inspection revealed that one fitting had been over-tightened while another was insufficiently tightened, and residual sealant debris was found on the internal threads of the manifold. After cleaning the threads and replacing the seals, the components were reinstalled according to the Aircraft Maintenance Manual (AMM), and the system was verified to be leak-free. The aircraft was released for flight.
Following a subsequent flight, the hydraulic leak reappeared in the same area. A secondary inspection by organization B identified that a pressure transducer had been incorrectly installed by organization A, specifically noting that two of the three mounting screws were loose. Once the transducer was correctly installed and the system was verified, no further leaks were observed during subsequent operations.