An anti-twist device for a sealing cap that is located on a fixed connecting piece of a motor vehicle radiator. The sealing cap comprises an external cap part with a grip element and a sealing element, which can be connected to a counter sealing element of the connecting piece and in relation to which the grip element can be rotated. The sealing cap also comprises an internal cap part comprising a valve assembly that is configured in an excess/negative pressure combination. An anti-twist stop acts in the external cap part between the grip element and the sealing element. An anti-twist device of this type has a no-load function instead of a locking function and yet has a simple construction and is easy to produce. To achieve this, the anti-twist stop can be actuated by means of a drive, which is controlled by the operating data in the container and is located inside said container in close proximity to the external cap part.