What does the term 'bleeding brakes' refer to in brake service work?

The term 'bleeding brakes' specifically refers to the process of withdrawing fluid from the brake system to remove trapped air. When air becomes entrained in the brake lines, it can lead to a spongy feel in the brake pedal and diminished braking capability. This air can prevent the brake fluid from properly transmitting pressure from the pedal to the brake components.

Bleeding the brakes involves opening a valve on the brake caliper or wheel cylinder and allowing the air bubbles to escape, often while simultaneously pressing the brake pedal. This process ensures that the brake fluid is free of air, restoring the efficiency and safety of the braking system.

The other options do not accurately describe the operation of bleeding brakes. Adding fluid to the system helps maintain fluid levels but does not specifically address the removal of air. Inspecting brake pads is critical for overall brake maintenance but is unrelated to the bleeding process. Testing brake pressure is part of evaluating brake system function but does not involve the removal of air from the brake lines. Hence, the selection related to withdrawing fluid to remove air is the correct understanding of 'bleeding brakes.'