2021 Mercedes-Benz AMG GT Brake Noise TSB

Mercedes-Benz has released Technical Service Bulletin (TSB) LI42.10-P-063502, version 8, dated January 17, 2025, to address complaints of brake noise and squealing in AMG vehicles. This TSB applies to all AMG models equipped with steel or ceramic brakes (option code B07), including the 2021 Mercedes-Benz AMG GT.

Symptoms

Owners may notice various noises and squealing from the service brake under different driving conditions and ambient temperatures. The TSB specifically lists the following symptoms:

• Chassis/suspension > Brake system > Service brake > Noises > General
• Chassis/suspension > Brake system > Service brake > Noises > Squeals
• Chassis/suspension > Brake system > Service brake > Noises > Whirring/howling
• Chassis/suspension > Brake system > Service brake > Noises > Makes noise

These noises are attributed to frictional vibrations within the brake system. The intensity of the noise can depend on speed, brake pressure, temperature, and air humidity.

Diagnosis

When diagnosing the Mercedes-Benz AMG GT brake noise, technicians are instructed to:

1. Check for any additional model-specific documents that might apply.
2. Attempt to reproduce the noise, ideally with the customer present during a test drive, to identify which axle or side the noise originates from.
3. Inspect the affected brake system components for wear, mechanical damage, or localized overheating.
4. If damaged components are found, they should be replaced before re-evaluating the noise.
5. With the vehicle on a lift, start the engine and depress the brake pedal 3-4 times. Then, check if each wheel turns freely by hand. Any wheel not turning freely must be addressed prior to further noise assessment.
6. Visually assess the condition of the brake rotors and pads, looking for signs of long periods of stagnation or other issues.

Repair Procedure Summary

The repair procedure involves specific steps for both front and rear axles, followed by a brake bedding process.

Front Axle Work

If the brake noise originates from the front axle, technicians will:

1. Remove the front brake linings.
2. Clean all contact points on the brake lining, caliper, and carrier.
3. Clean the bonding surface where the pistons contact the back of the brake pad. Apply adhesive film (3M F9469PC or A 190 423 32 00) to the backplate of the piston-side brake lining. For 6-piston calipers, the film is applied only in the center piston area. For other caliper configurations, it's applied where the piston(s) makes contact.
4. After installing the brake linings, actuate the brake for 30 seconds.

Rear Axle Work

If the brake noise comes from the rear axle, the procedure includes:

1. Removing the rear brake pads.
2. Cleaning all contact points on the brake lining, caliper, and carrier.
3. Greasing specific contact points (red areas in diagrams) between the brake lining and the guide of the brake caliper with heat-resistant lubricating paste (A001 989 87 51).
4. Cleaning the bonding surface and applying adhesive film (3M F9469PC or A 190 423 32 00) to the backplate of the piston-side brake lining.

Important Warnings

IMPORTANT: Technicians must be absolutely certain not to allow any lubricating paste to get between the friction surfaces of the brake pad and disc. This is crucial to ensure proper brake function and prevent further issues with the Mercedes-Benz AMG GT brake noise.

Brake Bedding Process

After the repair, a specific brake bedding process is required:

1. Confirm with the customer that approximately 30 miles will be driven before the next trip.
2. Select a suitable route to allow speeds of approximately 65 MPH.
3. Brake the vehicle 15 times from 62 MPH down to 30 MPH, using approximately 30 bar of brake pressure. This should be done without emergency stops and outside the ESP control range. Maintain a cooling distance of approximately 1 mile between each brake application.
4. Finally, drive approximately 3 miles to allow the system to cool completely.
5. Reassess the brake noise.

Required Tools or Parts

Technicians will need the following parts for this repair:

• 3M F9469PC: Alternate Adhesive Transfer Tape (sourced locally)
• A001 989 87 51: Heat-resistant lubricating paste (<1 quantity)
• A 190 423 32 00: Adhesive Transfer Tape (may be modified to fit or an alternate used)

Owner Action

If you are experiencing brake noise or squealing in your 2021 Mercedes-Benz AMG GT, it is recommended to visit an authorized Mercedes-Benz service center. They can perform the diagnostic steps and apply the necessary repair procedures outlined in TSB LI42.10-P-063502 to resolve the issue.

Source: NHTSA ID 11013081