The invention relates to a closure cap (10) for a stationary reservoir neck, especially of an automotive radiator. Said cap has a cap outer part (16) and a cap inner part (15), and the cap outer part (16) comprises a closure element (17) for the reservoir neck and a grip element (18) that permits it to be rotated relative thereto. A torsional stop (19) is provided between the grip element and the closure element (17) of the cap outer part (16). The torsional stop (19) that can be/is engaged under the action of a spring can be disengaged by a thermally or pressure-controlled drive (14). Said drive (14) is disposed in a zone of the cap inner part (15) facing the reservoir interior. A mechanical motion transfer device (70) is arranged between the drive (14) and the torsional stop (19) and extends off-set from the central axis of the closure cap (10).