a dampener for devices such as a leveling valve in which the dampener is a separate self - contained member formed of a piston cylinder part and a cap connected to each other and having a piston mounted in the chamber between the parts . the cylinder chamber occupied by the piston contains a viscous fluid that passes over the edge of the periphery of the inner wall of the chamber as the piston is moved from one end to the other . the two parts of the dampener are preferably constructed of transparent material so that it can be determined whether the space between the piston and the walls of the chamber is completely filled with a viscous fluid or whether there are any air bubbles or the like in the chamber . a temporary opening is provided in the cylinder cap for escape of air when the two parts are connected together . extending from both sides of the piston are hubs exposed to the exterior of the dampener . a plunger extends through a bore in the piston and the hubs , the piston being interconnected to the plunger by a stop means extending radially from the plunger . the hubs are provided so that coil springs circumventing the plunger can be utilized for containing the plunger in a neutral position . the total plunger movement is limited by the distance of the travel within the dampener .