what can cause the brake pedal on my BMW X3 F25 (2011-2018) to feel spongy

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface with the parking brake engaged.
• Wear safety gloves and goggles.

2. Inspect and Fill Brake Fluid

• Open the hood and locate the master cylinder reservoir.
• Check the brake fluid level; if low, top it up with manufacturer-recommended brake fluid (DOT 4).
• Inspect for any signs of contamination in the fluid.

3. Address Leaks

• Visually inspect brake lines, calipers, and wheel cylinders for any signs of leakage.
• If leaks are found, replace damaged lines or components as necessary.
• Use a wrench to tighten any loose fittings.

4. Bleed Brake System

• Start at the furthest brake from the master cylinder (usually the right rear wheel).
• Attach a clear hose to the bleeder valve and place it in a container.
• Have an assistant pump the brake pedal several times, then hold it down.
• Open the bleeder valve to release air and fluid, then close it before your assistant releases the brake pedal.
• Repeat until no air bubbles appear in the fluid.
• Move to the next brakes in order (left rear, right front, left front).

5. Test Brake Booster

• With the engine off, press the brake pedal several times to exhaust the vacuum.
• Start the engine and press the pedal; it should drop slightly. If it does not, the brake booster may be faulty and require replacement.

6. Final Check

• Reinspect brake fluid levels after bleeding.
• Test drive the vehicle to ensure the brakes feel firm and responsive.