Check valve

A check valve for a fluid circuit of a motor vehicle, comprising a casing delimiting an internal volume provided with an inlet, an outlet and defining a main axis X of flow of fluid between the inlet and the outlet through the casing, a membrane element, extending at least partially inside the internal volume of the casing, the membrane element having a contact portion radially elastically deformable between a sealing position wherein the contact portion contacts an internal wall of the internal volume and a fluid opening position wherein the fluid can flow from the inlet to the outlet around the membrane element, wherein the membrane element axially has a decreasing cross section between a proximal end portion forming the contact portion and an opposite distal end portion, the casing comprises on the inlet side an internal seat for receiving the distal portion and on the outlet side an axial extension pin configured to extend inside the proximal portion of the membrane element such that the membrane element is immobilized axially between the seat and the pin.