Crankcase venting system comprising an oil separator arranged in a housing that separates the housing into an unfiltered air side and a filtered air side, wherein in the area of the unfiltered air side a valve is arranged that is comprised of a valve plate, a pressure spring resting against the valve plate, as well as a valve seat that is closed or opened by means of the valve plate, and wherein the valve is closed off by a lid that is locked or snapped in place.