EN 215 requires thermal and mechanical endurancee tests as well as the verification of mechanical properties of thermostatic radiator valves. To expose the head of thermostatic radiator valves to a permanent thermal load, the head is mounted on a device, and the stroke movement of the stem is registered. An automatic control unit immerses the head alternately in water baths of different temperatures until the required number of immersions has been reached. An automatic mechanical turning gear produces the constant mechanical load. The thermostatic radiator valve is connected to a closed water circuit. The head is mounted on a device which is able to carry out defined forward and backward movements on the temperature selector. An automatic control unit carries out these turning movements alternately until the required mechanical load has been achieved. During the process, the temperature of the circulated water is controlled and kept at a constant level.