how to fix brake pedal that goes to the floor in my BMW 5 Series F10/F11 (2010-2017)?

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is on a flat surface and securely lifted with jack stands.
• Disconnect the battery to avoid electrical issues.

2. Inspect and Replace Brake Fluid

• Tools Required: Brake fluid, funnel, clean rags.
• Check the brake fluid reservoir; if the fluid is low or contaminated, drain the old fluid.
• Refill with high-quality brake fluid (DOT 4 recommended).

3. Inspect and Replace Brake Lines

• Tools Required: Socket set, brake line wrench, new brake lines.
• Check for leaks or damage in the brake lines; if found, replace with new lines.
• Use a brake line wrench to loosen and remove the affected line, then install the new line and torque to manufacturer specifications.

4. Check and Replace the Master Cylinder

• Tools Required: Socket set, line wrenches, new master cylinder, brake fluid.
• Disconnect the brake lines from the master cylinder using line wrenches to avoid damage.
• Remove the master cylinder mounting bolts and detach the cylinder.
• Install the new master cylinder, ensuring proper alignment, and torque the bolts to specifications.
• Reconnect brake lines and refill the system with brake fluid.

5. Bleed the Brake System

• Tools Required: Brake bleeder kit or hose, container for old fluid.
• Have an assistant pump the brake pedal several times and hold it down.
• Open the bleeder valve on the farthest brake caliper from the master cylinder, allowing fluid and air to escape.
• Close the valve and have the assistant release the brake pedal; repeat until no air bubbles are present.
• Move to the next caliper and repeat the process until all calipers are bled.

6. Check Brake Booster

• Tools Required: Vacuum gauge (if needed).
• Inspect the brake booster for signs of vacuum leaks (listen for hissing).
• If the booster is faulty, remove it by disconnecting the vacuum line and mounting bolts, then replace it.