The present invention relates to a cooling system valve (24) for an internal combustion engine cooling system (12), the internal combustion engine cooling system (12) comprising a radiator (14) and a coolant passage (16) adapted to cool at least a portion of an internal combustion engine (18), the cooling system valve (24) being adapted to be located between the radiator (14) and the coolant passage (16), as seen in an intended direction of flow from the radiator (14) to the coolant passage (16). The cooling system valve (24) is adapted to automatically assume each one of at least the following conditions: —an open condition, allowing coolant transport from the radiator (14) towards the coolant passage (16) via the cooling system valve (24), and —a closed condition, preventing coolant transport in a direction from the coolant passage (16) towards the radiator (14) via the cooling system valve (24).