why is my Volvo XC90 buzzing when I press the brake pedal

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a level surface and securely supported with jack stands.
• Disconnect the battery to avoid any electrical shorts.

2. Check Brake Fluid Level

• Remove the brake fluid reservoir cap.
• Inspect fluid level; top off with the appropriate type of brake fluid (DOT 4 or as specified by the manufacturer) if low.
• Reinstall the cap securely.

3. Inspect Brake Components

• Remove the wheel and tire assembly to access the brake assembly.
• Check the brake pads for thickness; replace if below manufacturer specifications (usually less than 3mm).
• Inspect brake rotors for grooves or warping; replace if necessary.

4. Test Brake Booster

• Disconnect the brake booster vacuum line and inspect for cracks or blockages.
• Start the engine and check for a hissing sound, which may indicate a leak.
• If the brake booster is faulty, replace it by removing the master cylinder first, then unmount the booster.

5. Reconnect Electrical Components

• Check the brake light switch for proper operation; replace if malfunctioning.
• Ensure all related electrical connections are clean and secure.

6. Reassemble and Test

• Reinstall the wheel and tire assembly.
• Reconnect the battery.
• Test drive the vehicle to ensure the buzzing sound has stopped and the brakes function correctly.