Patent ID: 8574106

Claim:
A hydraulic tensioner for a traction element drive of an internal combustion engine, comprising a tensioner housing having a bore, a hollow piston located in the bore, the hollow piston having a piston head that extends out from the housing, with a pressure relief opening defined through the piston head, a check valve located in the bore along a pressurized fluid path to the hollow piston, and a tensioning spring extending from the bore inside the hollow piston toward the piston head, and a pressure relief valve located within the hollow piston adjacent to the piston head, the pressure relief valve including a valve body having a flange with a support surface that rests against an inside of the piston head and a hollow spring guide that extends from the flange toward the base of the bore, a valve seat is formed in the hollow spring guide, a spring is located in the hollow spring guide and biases a valve ball against the valve seat, at least one of the support surface of the flange, or the valve seat include surface irregularities that allow gas venting through the pressure relief valve.