A collector tank for a heat exchanger of an automotive cooling system includes a one-piece tank element comprising a first collecting region and a second collecting region, wherein at least one of the first collecting region and the second collecting region comprises a projection; a base that closes off the collecting regions of the tank element, the base comprising at least one channel; a sealing element disposed within the at least one channel; and a stress generating means located adjacent to the channel and clamping at least a portion of the one-piece tank element to the base such that the sealing element is compressed between the projection and the base within the channel. The stress generating means is a means selected from the group consisting of a tensile stress generating means, a compressive stress generating means, and a combination thereof.