A valve assembly for a tank of a vehicle is disclosed. A valve body is adapted to be attached to the tank. A seat is disposed inside the valve body and defines an outlet for venting the tank. A float is disposed inside the valve body and is movable between a first position and a second position relative to the valve body in response to a liquid fluid level inside the tank. A support is coupled to the float and is movable with the float between the first and second positions. A sealing member is attached to the support and has an engagement portion supported by a base to define a space between the engagement portion and the support to allow movement of the engagement portion between an initial position when in the first position and a displaced position when in the second position.