A hydraulic tensioner (10) having a porous vent (70) formed of sintered powder metal adapted to permit air to readily escape from within the tensioner (10) while inhibiting air ingestion during cycling and limiting oil leakage. The vent (70) is located within an aperture (46) of the plunger (40) near the highest point of the tensioner or at the top of the spring (60) within the interior space of the plunger (40). Alternatively, the air vent (70) may be located at the oil supply inlet (24) before the oil enters the tensioner's fluid chamber (22).