An apparatus for sealing a valve

Disclosed is an apparatus for sealing a valve for controlling a coolant of an internal combustion engine of a motor vehicle, which is installed with a valve housing (1) in a cooling system, wherein the valve housing (1) contains the inlet side and / or outlet side a sealing ring (3) having a annular wall (4) and one of the annular wall (4) of a contact point (6) outgoing, objectionable annular lip (5).