In a hydraulic system, what is the primary purpose of a reservoir?

• A. To pressurize the system
• B. To store hydraulic fluid, allow air separation, and help with cooling
• C. To filter contaminants
• D. To drive the pump

Answer: (B)

In a hydraulic system, the reservoir’s main job is to store hydraulic fluid and provide space for air to separate from the oil, while also helping remove heat. Storing fluid ensures the pump always has a ready supply so suction isn’t compromised as fluid expands and contracts with temperature changes. As oil circulates and becomes aerated, the reservoir allows air bubbles to rise and disengage rather than being carried through the system, which helps prevent cavitation and poor performance. The surface area of the reservoir and the possible cooling features or passive cooling from air exposure help dissipate heat, keeping the oil at a workable temperature and maintaining proper viscosity. While other components handle pressurizing, filtering, or driving the pump, the reservoir’s primary role is to hold fluid, separate air, and assist in cooling, making it the best fit for the question.