Abstract: The invention concerns an oil separator (2) for crankcase gases of an internal combustion engine, comprising a preliminary separator (28), a cyclone separator (30), a fine separator (32) and, if necessary, a valve device (36) that are provided in a cascade arrangement on a cylinder-head cover (4) of the internal combustion engine; in order to simplify the design of the oil separator and obtain easier installability, it is provided that the preliminary separator (28), the cyclone separator (30), the fine separator (32) and the valve device (36) provided, if necessary, are located on the outside (20) of the cylinder-head hood (4) and are covered by a housing half-shell (6) which, together with the outside (20) of the cylinder-head hood (4), forms a housing for the oil separator (2).

Abstract: The invention concerns an oil separator (2) for crankcase gases of an internal combustion engine, comprising a preliminary separator (28), a cyclone separator (30), a fine separator (32) and, if necessary, a valve device (36) that are provided in a cascade arrangement on a cylinder-head cover (4) of the internal combustion engine; in order to reduce the mutual interference of flowing crankcase gas and separated fluid, an oil drain opening (44) is provided upstream from the cyclone separator (30) in the flow or cascade direction, through which oil separated in the preliminary separator can be returned.