This hydraulic pump O-ring seals the interface between the pump housing and its cover or mounting flange. It prevents pressurized hydraulic fluid from leaking at the joint, maintaining system pressure and preventing aeration of the fluid. A degraded or hardened O-ring allows external leakage, which reduces pump output and can introduce air into the circuit, leading to noisy operation and erratic implement response. This original AGCO part is molded to the same cross-section and durometer as the factory seal, ensuring it seats correctly in the groove and compresses to the proper squeeze for a leak-free joint. Replace the O-ring whenever the pump is removed or the housing is opened; lubricate the seal with clean hydraulic fluid before installation to prevent rolling or pinching.