An exemplary door closer includes a housing defining a hydraulic chamber having a hydraulic fluid disposed therein. A pinion is rotatably mounted to the housing and extends into the hydraulic chamber. A piston is mounted for reciprocal movement within the housing, and defines a rack engaged with the pinion. The housing further defines an aperture in fluid communication with the hydraulic chamber. A regulating screw is rotatably mounted within the aperture such that rotation of the regulating screw in a first direction advances the regulating screw into the hydraulic chamber and such that rotation of the regulating screw in an opposite second direction withdraws the regulating screw away from the hydraulic chamber. A stop member is mounted in the aperture such that the stop member limits withdrawing movement of the regulating screw to thereby prevent leaking of the hydraulic fluid from the hydraulic chamber via the aperture.