Abstract: A cap assembly is provided for a container that defines a reservoir for power steering fluid. The cap assembly has an outer cap adapted to be secured to an open mouth of the container and an inner cap secured to the outer cap and adapted to extend through the open mouth into a neck of the container. The inner cap has an O-ring adapted to seal against a neck of the container. A build-up of air in the reservoir is vented to the outside atmosphere through a passageway in the cap assembly. A filter in the passageway is adapted to pass the air but not to pass a mist emanating from the power steering fluid.