Methods and systems for reducing a flow of ambient air into a bearing lubricating oil system are provided. The system includes a lubricating oil bearing cover that is stationary with respect to the bearing wherein the bearing is configured to support a portion of a rotatable machine shaft. The cover includes a first end cap extending radially inwardly towards the shaft such that a cavity surrounding the bearing is formed by the cover and the first end cap and a set of seal rings positioned substantially concentric with the shaft and forming a seal against lubricating oil flow. The seal rings include a plurality of wire bristles extending radially inwardly from the end cap wherein the wire bristles are configured to extend to a surface of the shaft when assembled and the bristles are configured to present a tortuous flow path to gas infiltrating the cavity.