A method and apparatus are disclosed for cooling damping fluid in a vehicle suspension damper unit. A damping unit includes a piston mounted in a fluid cylinder. A bypass fluid circuit having an integrated cooling assembly disposed therein is fluidly coupled to the fluid cylinder at axial locations that, at least at one point in the piston stroke, are located on opposite sides of the piston. The cooling assembly may include a cylinder having cooling fins thermally coupled to an exterior surface of the cylinder and made of a thermally conductive material. The bypass channel may include a check valve that permits fluid flow in only one direction through the bypass channel. The check valve may be remotely operated, either manually or automatically by an electronic controller. A vehicle suspension system may implement one or more damper units throughout the vehicle, controlled separately or collectively, automatically or manually.