Method and device for testing the tightness of the main air supply line in railway vehicles

The method involves determining pressure drop of volumes of a main air pipeline (5) in a railway vehicle (6) associated to supplementary volumes of pipe and hose lines. The pipeline is evaluated as sealed during comparison of a smaller resultant pressure drop with a maximum allowable pressure drop. The pipeline is evaluated as untight during comparison of a larger resultant pressure drop with the maximum allowable pressure drop. An independent claim is also included for a brake test device for testing air tightness of a main air pipeline of a railway vehicle.