A lubricant reservoir comprising: a housing defining a reservoir; an actuator disposed within the housing and dividing the reservoir into an upper portion and a lower portion, wherein the actuator includes a top side, a bottom side, and a bore extending through the actuator between the top side and the bottom side, and wherein the actuator is movable within the housing in response to a changing lubricant level and to alter a first volume of the upper portion and a second volume of the lower portion; characterized in that a vent valve disposed within the bore movable with the actuator, wherein the vent valve is normally open to allow air to pass through the bore between the lower portion and the upper portion-and is actuated to a closed state by a rising level of lubricant in the lower portion to prevent lubricant from passing from the bottom side to the top side through the bore, and wherein the vent valve comprises: a valve seal disposed within the bore proximate a top side of the actuator; a ball disposed at least partially within the bore; a retaining member configured to interface with the ball to maintain the ball at least partially within the bore, the ball disposed at least partially between the retaining member and the valve seal ; wherein the vent valve is normally open and is actuated to the closed state by the rising level of lubricant in the lower portion; wherein the vent valve being in the closed state prevents the lubricant from flowing from the lower portion to the upper portion to allow the lubricant to exert a biasing force on the actuator to displace the actuator upward within the housing . a housing defining a reservoir; an actuator disposed within the housing and dividing the reservoir into an upper portion and a lower portion, wherein the actuator includes a top side, a bottom side, and a bore extending through the actuator between the top side and the bottom side, and wherein the actuator is movable within the housing in response to a changing lubricant level and to alter a first volume of the upper portion and a second volume of the lower portion; characterized in that a vent valve disposed within the bore movable with the actuator, wherein the vent valve is normally open to allow air to pass through the bore between the lower portion and the upper portion-and is actuated to a closed state by a rising level of lubricant in the lower portion to prevent lubricant from passing from the bottom side to the top side through the bore, and wherein the vent valve comprises: a valve seal disposed within the bore proximate a top side of the actuator; a ball disposed at least partially within the bore; a retaining member configured to interface with the ball to maintain the ball at least partially within the bore, the ball disposed at least partially between the retaining member and the valve seal ; a valve seal disposed within the bore proximate a top side of the actuator; a ball disposed at least partially within the bore; a retaining member configured to interface with the ball to maintain the ball at least partially within the bore, the ball disposed at least partially between the retaining member and the valve seal ; wherein the vent valve is normally open and is actuated to the closed state by the rising level of lubricant in the lower portion; wherein the vent valve being in the closed state prevents the lubricant from flowing from the lower portion to the upper portion to allow the lubricant to exert a biasing force on the actuator to displace the actuator upward within the housing . <EOS>