Massage the radiator valve by following these steps. Remove the thermostat with an Allen key or by turning counterclockwise (on newer models). Gently push in on the exposed radiator valve pin with the flat end of the Allen key. The pin should move in 2-3mm and bounce out again. If the radiator thermostat valve pin is stuck, gently alternate between tapping the valve’s side and moving the pin in and out until it frees. Check for leaks and reattach the thermostat.