Rotating coalescer crankcase ventilation (CV) systems are described. The described CV systems utilize a pumping pressure created by the porous media of the rotating coalescer to maintain positive recirculation of filtered blowby gases through a potential leak gap between a static housing inlet and a spinning component of the rotating coalescer. In some arrangements, the porous media is fibrous media. The filter media may be pleated or non-pleated. The positive recirculation caused by the pressure balance prevents unfiltered blowby gases from bypassing the media of the rotating coalescer from the upstream side to the downstream side of the filter media through the gap. During operation, the pressure balance between the upstream side and downstream side of the filter media maintains the positive recirculation, which in turn maintains a high filtration efficiency.