Sealing cap for a motor vehicle radiator

Pressure cap (10, 110, 210) for a fixed neck of a tank, in particular an automobile radiator, is provided with an outer cap component (16) and an inner cap component (15) which has a flow connection between the inside and the outside of the tank and a valve arrangement (11) for releasing and blocking the flow connection, whereby said valve arrangement (11) has an axially movable pressure-relief valve body (12) which toward the inside of the tank is pressed against a sealing seat on the inner cap component (15) with a bias controlled by the operating pressure, such that when the pressure inside the tank exceeds a threshold value, the pressure-relief valve body (12) can be lifted off the sealing seat, and whereby the said valve arrangement (11) has a vacuum valve body (13), characterized in that the bias with which the pressure-relief valve body (12) is pressed against the sealing seat can be adjusted by means of a thermal drive (14) in the form of an expansion-material membrane capsule (50) which is provided with a temperature sensor (54) which passes through the cap axis and extends into the neck of the tank, and that the vacuum valve body (13) is arranged eccentrically in relation to the cap axis.