2021 Mercedes-Benz AMG GT Brake Noise TSB

Owners of 2021 Mercedes-Benz AMG GT vehicles may experience various noises from their service brakes, such as squealing, whirring, howling, or general brake noise. Mercedes-Benz has released Technical Service Bulletin (TSB) LI42.10-P-063502, dated July 24, 2025, to provide guidance for diagnosing and resolving these issues.

Symptoms

The primary complaint addressed by this TSB is Mercedes-Benz AMG GT brake noise. Owners may notice:

• Noises or squealing from the service brake in various driving situations.
• General brake noises.
• Specific squealing sounds.
• Whirring or howling noises during braking.

These symptoms are categorized under "Chassis/suspension > Brake system > Service brake > Noises" in Mercedes-Benz's diagnostic system.

Diagnosis and Trigger Conditions

The TSB explains that high-performance AMG brakes are designed for demanding conditions and can emit noise in certain scenarios due to frictional vibrations. Factors contributing to this Mercedes-Benz AMG GT brake noise include:

• Driving style: Aggressive or frequent braking.
• Brake pressure and application style: Consistent low brake pressure, often referred to as "riding brakes," which can prevent brakes from cooling sufficiently, especially in stop-and-go traffic.
• Ambient temperatures: Environmental conditions can influence brake noise.

Technicians are instructed to begin diagnostics by:

1. Reproducing the complaint and identifying the specific axle or side where the noises occur, ideally with the customer present.
2. Checking the brake system for component wear, mechanical damage, or localized overheating. Damaged components should be replaced.
3. Assessing the condition of brake rotors and pads according to Workshop Information System (WIS) guidelines, including visual inspection for issues like prolonged stagnation.
4. Cleaning brake components to remove dust and debris.
5. Securing the vehicle on a lift, starting the engine, and depressing the brake pedal 3-4 times. Each wheel must then be checked to ensure it turns freely by hand. If a wheel does not turn freely, this must be resolved before proceeding with noise assessment.
6. Checking for additional documents specific to the model that might offer further guidance.

Repair Procedure Summary

The repair procedure focuses on reducing or eliminating frictional vibrations in the brake system. It involves specific steps for both front and rear axles, along with a crucial brake bedding process. Technicians must be absolutely certain not to allow paste between the friction surfaces of the pad and disc. If a brake pad already has a metal backing plate, adhesive film is not needed.

For the Front Axle:

1. Remove the front axle brake linings.
2. Clean all contact points on the brake lining backing plate, guide pins, and caliper/carrier.
3. Clean the bonding surface where pistons contact the brake pad. Apply adhesive film to the backplate of the piston-side brake lining. If adhesive is already present, it may be carefully scraped off and a new adhesive applied, or Molykote may be used instead.
4. Chamfer the edges of the brake pads, gently rounding off sharp leading edges. Pads with vertical grooves can be chamfered with a triangular file. This process is illustrated in the "Chamfering Technique" attachment.
5. Apply Molykote to the sides of the backing plate, as shown in the "Adhesive and Paste Application Area" attachment.
6. After installing the brake linings, actuate the brake for 30 seconds.

For the Rear Axle:

1. Remove the rear axle brake pads.
2. Clean all contact points on the brake lining backing plate and caliper/carrier.
3. Clean the bonding surface where pistons contact the brake pad. Apply adhesive film to the backplate of the piston-side brake lining.
4. Chamfer the edges of the brake pads, similar to the front axle procedure.
5. Grease the contact points (highlighted in red in the "Rear Pad Grease Area" attachment) between the brake lining and the guide of the brake caliper with Molykote.

Brake Bedding Process:

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

1. Clarify with the customer that approximately 30 miles of driving will be incurred.
2. Select a suitable route to achieve speeds of approximately 65 MPH.
3. For AMG P3 Hybrid vehicles, switch off recuperation before bedding in the brakes.
4. Brake the vehicle 15 times from 62 MPH down to 30 MPH, maintaining approximately 30 bar of brake pressure (monitored via XENTRY). Ensure no emergency stops and avoid braking within the ESP control range. Maintain a cooling distance of about 1 mile between each brake application.
5. Finally, drive approximately 3 miles to allow the system to cool.
6. Reassess the brake noise.

Required Tools or Parts

To perform this repair, specific materials are needed:

• 3M F9469PC: Alternate Adhesive Transfer Tape (Quantity 1, sourced locally).
• A 001 989 87 51 09: Molykote (Quantity <1).
• A 190 423 32 00: Adhesive Transfer Tape (Quantity 1, may require modification or an alternate).

Owner Action

If you are experiencing Mercedes-Benz AMG GT brake noise, it is recommended to contact an authorized Mercedes-Benz service center. They can perform the diagnostic steps and apply the repair procedure outlined in TSB LI42.10-P-063502. This ensures that your vehicle's brakes are serviced according to manufacturer specifications, addressing the frictional vibrations causing the noise.

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NHTSA ID: 11021141