Which of the following is NOT a procedure for removing air from a hydraulic system?

Bench bleeding is not considered a procedure for removing air from a hydraulic system in the context of servicing vehicles. Instead, it is a method used primarily for bleeding air from brake components, such as master cylinders, before they are installed on a vehicle to ensure that any air trapped inside does not enter the hydraulic brake system during installation.

Power bleeding, manual bleeding, and vacuum bleeding, on the other hand, are all recognized procedures specifically designed for effectively removing air from hydraulic brake systems.

Power bleeding uses a pressure source to push brake fluid through the system, which helps dislodge and push out any trapped air. Manual bleeding relies on the act of a person pumping the brake pedal and then opening bleeder screws to allow air to escape while fluid flows through. Vacuum bleeding utilizes a vacuum pump to create a low-pressure environment that draws brake fluid through the system, removing air in the process.

These techniques are commonly used in maintenance and repair to ensure that the hydraulic system operates effectively without the presence of air, which can compromise braking performance.