how to fix my BMW 3 Series F30/F31 (2012-2019) brake pedal going to the floor?

Solution

1. Preparation

• Gather all necessary tools and parts.
• Ensure the vehicle is parked on a level surface and the engine is off.
• Wear safety goggles and gloves for protection.

2. Check and Replenish Brake Fluid

• Tools Required: Brake fluid, funnel
• Instructions:
  1. Open the hood and locate the brake fluid reservoir.
  2. Check the fluid level; if low, add the recommended brake fluid (typically DOT 4 for BMW).
  3. Close the reservoir cap securely.

3. Inspect and Repair Leaks

• Tools Required: Wrench set, brake line wrench, replacement brake lines (if necessary)
• Instructions:
  1. Inspect brake lines, calipers, and master cylinder for leaks.
  2. Tighten any loose fittings or connections.
  3. Replace any damaged brake lines or components as needed. Ensure all connections are secure.

4. Bleed the Brake System

• Tools Required: Brake bleeder kit, clear tubing, container
• Instructions:
  1. Start with the wheel farthest from the master cylinder (usually the passenger rear).
  2. Attach the clear tubing to the bleeder valve on the brake caliper and place the other end in a container.
  3. Have an assistant pump the brake pedal several times and hold it down.
  4. Open the bleeder valve to allow brake fluid and air to escape.
  5. Close the valve before the assistant releases the brake pedal.
  6. Repeat this process until no air bubbles are seen in the fluid stream.
  7. Move to the next wheel and repeat the bleeding process in the correct order (passenger rear, driver rear, passenger front, driver front).

5. Inspect and Replace Master Cylinder (if needed)

• Tools Required: Wrench set, brake fluid, new master cylinder (if required)
• Instructions:
  1. Disconnect the brake lines from the master cylinder using a brake line wrench.
  2. Unbolt the master cylinder from the brake booster.
  3. Remove the master cylinder and replace it with the new one.
  4. Reconnect the brake lines and torque to manufacturer specifications.
  5. Refill the brake fluid reservoir and bleed the brake system again.