Which outcome is achieved by performing a hydraulic reservoir drain and bleed procedure correctly?

• A. To remove old fluid, contaminants, and air from the system and ensure proper filling and pressure.
• B. To seal leaks permanently.
• C. To replace the entire hydraulic system.
• D. To increase fluid color.

Answer: (A)

Removing old hydraulic fluid, contaminants, and air from the reservoir and then properly refilling and bleeding the system is the essential outcome of a drain-and-bleed procedure. Old fluid can carry particulates and moisture that degrade performance, while air in the lines compresses and creates spongy, inconsistent controls. By draining, you refresh the fluid by removing the degraded material, and by bleeding, you purge air pockets so the hydraulic circuit fills completely with fluid and reaches the correct pressure. This helps deliver smooth, reliable operation and protects components from cavitation or erratic response.

This procedure isn’t about sealing leaks, replacing the entire hydraulic system, or changing fluid color. Leaks require repair, replacing the system isn’t the goal of a drain-and-bleed, and color change has no functional purpose in this context.