my BMW 3 Series E90/E91 (2005-2012) brake pedal goes to the floor why is that

Solution

1. Preparation

• Gather necessary tools and parts, ensuring the vehicle is parked on a level surface.
• Wear safety glasses and gloves.
• Ensure the vehicle is securely supported using jack stands if lifting is necessary.

2. Inspect and Replace Damaged Components

• Sub-step 1: Locate the master cylinder and check for leaks. If leaking, replace the master cylinder.
  • Tools Required: Wrench set, fluid catch pan.
• Sub-step 2: Inspect all brake lines and hoses for signs of wear or leaks. Replace any damaged lines.
  • Tools Required: Line wrench, cutting tool, new brake line or hose.

3. Bleed the Brake System

• Sub-step 1: Start with the wheel farthest from the master cylinder (usually the right rear).
  • Attach a clear hose to the bleeder valve on the brake caliper.
• Sub-step 2: Have an assistant press the brake pedal while you open the bleeder valve to release air and fluid. Close the valve before your assistant releases the pedal.
• Sub-step 3: Repeat this process for all four wheels, moving from the farthest to the closest to the master cylinder (right rear, left rear, right front, left front).
• Tools Required: Brake bleeder kit or clear tubing, wrench for bleeder valves.

4. Refill Brake Fluid

• Sub-step 1: After bleeding, check the brake fluid reservoir and refill with the recommended brake fluid (DOT 4 for most BMWs).
• Sub-step 2: Ensure the reservoir cap is securely closed to avoid moisture contamination.
• Tools Required: Funnel, brake fluid.