why does my BMW 5 Series G30/G31 (2017-2024) make a hissing noise when I start the engine?

Solution

1. Preparation

• Tools Required: OBD-II scanner, mechanic's stethoscope, vacuum gauge, flashlight, socket set.
• Safety Warnings: Disconnect the battery before working on any electrical components. Allow the engine to cool before inspection.

2. Inspect and Replace Vacuum Hoses

1. Locate Vacuum Hoses: Identify all vacuum hoses connected to the intake system.
2. Check for Damage: Look for any signs of wear, cracks, or disconnections.
3. Replace Damaged Hoses: If any hoses are damaged, remove them using a socket set and replace with OEM parts. Ensure all clamps are tight.
4. Reattach Hoses: Reconnect all hoses securely and verify their routing.

3. Repair or Replace Intake Manifold

1. Remove Engine Cover: Use a socket set to remove the engine cover and access the intake manifold.
2. Inspect Manifold Gasket: Check the intake manifold gasket for wear or damage; replace if necessary.
3. Reinstall Manifold: If the gasket was replaced, reinstall the manifold using the correct torque specifications (typically around 10-15 Nm, but refer to service manual).
4. Reconnect All Components: Ensure all related components are reattached correctly.

4. Examine and Repair PCV System

1. Locate PCV Valve: Identify the location of the PCV valve in the engine bay.
2. Check Functionality: Remove the PCV valve and shake it; it should rattle. If it does not, replace it.
3. Inspect Hoses: Check hoses connected to the PCV system for cracks or leaks; replace if necessary.
4. Reinstall and Test: Reinstall the PCV valve and hoses securely.