Washing device for a rear glass pane in a motor vehicle

The device has an aerodynamic spoiler (5) with a hollow body (7) in two portions (8, 9). The portion (9) is movably mounted in a plane relative to the portion (8) to arrange a transversal slit (11) in between them. External air flowing to the spoiler is sucked via the slit for being displaced to a glass pane. The portion (9) supports a nozzle (19) connected to the portion (8) by a washing water supply duct. The washing water supply duct controls and combines relative displacement of the portions generated by the pressure of the water admitted in the duct.