Abstract: A self-closing valve is provided at a zone of a circumferential wall section of its housing that bounds a relief chamber with a stripping and holding-back arrangement which includes a saw-tooth formation constituted by a plurality of teeth and is situated at an end portion of the wall section that is close to the inlet of the valve housing. The teeth of the formation have respective substantially radially extending flanks and steep inclined flanks which are operative for stripping off contaminant particles which are entrained for joint movement by a sealing lip of a piston seal that is mounted for joint movement on a valve piston received in the wall section from the sealing lip during the movement of the valve toward its closing position, and for holding such contaminant particles back during the movement of the valve piston towards its open position.