why does my BMW 5 Series G30/G31 (2017-2024) brake pedal feel spongy?

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is on a level surface and securely lifted with jack stands if needed.
• Wear safety gloves and goggles.

2. Check Brake Fluid Level

• Tools Required: Brake fluid container, funnel
• Inspect the brake fluid reservoir and top off with the appropriate brake fluid (DOT 4 recommended for BMW).
• Check for any signs of contamination in the fluid.

3. Inspect for Leaks

• Visually inspect all brake lines, hoses, and connections for signs of fluid leaks.
• If leaks are found, replace the damaged section of the line or component.

4. Bleed the Brake System

• Tools Required: Brake bleeder kit, clear tubing
• Attach tubing to the bleeder valve on each brake caliper.
• Begin with the caliper furthest from the master cylinder and work towards the closest.
• Open the bleeder valve and have an assistant press the brake pedal until fluid runs clear, then close the valve.
• Repeat until no air bubbles are present in the fluid.

5. Check Brake Components

• Tools Required: Socket set, torque wrench
• Remove wheel to access brake components.
• Inspect brake pads for wear; replace if less than 3mm thickness remains.
• Check rotors for warping or scoring; replace if necessary.

6. Test Brake Booster

• Tools Required: Vacuum gauge
• Start the engine and listen for hissing sounds indicating a vacuum leak.
• Use a vacuum gauge to check the brake booster for adequate vacuum pressure; replace the booster if it fails to hold vacuum.