2023-2024 BMW Intermittent Humming Noise SIB 64 01 25

Owners of certain 2023-2024 BMW models may experience an intermittent "humming" or "foghorn" type sound emanating from their vehicle. This low hum typically lasts for only a few seconds and can occur while the engine is running or up to an hour after the engine has been shut down. BMW has released Service Information Bulletin SIB 64 01 25 to provide technicians with guidance on diagnosing and resolving this specific concern.

Symptoms: Intermittent Humming Noise

The primary symptom addressed by BMW Service Information Bulletin SIB 64 01 25 is an intermittent "humming" or "foghorn" type sound. This noise is described as a low hum that lasts for a brief period, typically only a few seconds. It can manifest under various conditions, including when the vehicle's engine is operating or even after the engine has been turned off, persisting for up to an hour.

BMW notes that other noises may occur in these vehicles, each with different root causes:

• A "whistling noise" heard above 40 mph, loudest with the sunroof in the vent position, is covered under SI B64 01 21.
• A "clicking noise" resulting from repeated activation of the recirculated air flap is addressed by SI B64 02 22.
• A "groaning noise" originating from within the heating and air-conditioning unit in the center of the instrument panel, caused by the movement of ventilation, air stratification, or recirculated air flaps, is covered under SI B64 04 22.

Cause of the BMW Intermittent Humming Noise

The intermittent humming noise is primarily attributed to the expansion valve within the air conditioning system. This component moves internally in response to changes in system pressure and temperature, which can occasionally generate noise. While some internal movement noise is normal, excessive noise indicates a potential issue that needs attention. This is the root cause of the BMW intermittent humming noise.

Repair Procedure Summary

To address the intermittent humming noise, technicians should follow a specific procedure outlined in SIB 64 01 25:

1. Confirm the Customer's Concern: The technician must first verify that the customer's description of the "humming" or "foghorn" type sound matches the issue.
2. Check for Stored Fault Codes: The vehicle should be scanned for any related diagnostic trouble codes (DTCs) that might provide further insight into the problem.
3. Perform Standard System Diagnosis: A comprehensive diagnosis of the air conditioning system should be conducted to pinpoint the exact cause of the noise.
4. Expansion Valve Replacement: The expansion valve should only be replaced if excessive noise is confirmed during diagnosis. If contamination is found within the air conditioning system during the expansion valve replacement, the entire system should be flushed to prevent future issues.

Important Warnings

BMW explicitly states that the expansion valve should only be replaced in cases where excessive noise occurs and is confirmed. This prevents unnecessary parts replacement and ensures that the repair directly addresses the verified concern. Technicians are also instructed to explain the cause of the noise to the customer, clarifying that the expansion valve's internal movement can occasionally produce sound.

Owner Action

If your 2023-2024 BMW is experiencing an intermittent humming noise or "foghorn" type sound, it is recommended to contact an authorized BMW service center. Describe the symptoms clearly to the service advisor. The technicians will use BMW Service Information Bulletin SIB 64 01 25 to diagnose and, if necessary, repair the issue under warranty terms if applicable.

Source: NHTSA ID: 11014665