When bleeding brakes using the gravity bleed method:

Prepare for the Automotive Service Technician Period 1 exam. Study with flashcards and multiple choice questions, each question has hints and explanations. Get ready for your exam!

Gravity bleed relies on brake fluid flowing downward from the master cylinder through the brake lines to the bleeding screws simply by gravity. The catch bottle is essential here because it collects the fluid as it exits each bleed screw, along with any air that escapes. This keeps old fluid and air out of the system, prevents spills on nearby parts, and lets you monitor for air bubbles so you know when that line is clear. It also makes it easier to keep the master cylinder reservoir topped up so air isn’t drawn back in. Using the reservoir cap to relieve pressure isn’t how this method is done, since the leak and flow are controlled at the bleed screws. Using compressed air to push fluid is not part of gravity bleeding and can introduce air or contaminate the system. Bleeding without a bottle risks splashing fluid, losing track of air in the line, and allowing air to be drawn back in.