2021 Mercedes-Benz AMG GT Brake Noise TSB

Symptoms

Owners of 2021 Mercedes-Benz AMG GT vehicles may experience various forms of brake noise from the service brake system. These noises can occur in different driving situations and ambient conditions. The reported symptoms include:

• 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

If you hear any of these sounds, it indicates a potential Mercedes-Benz AMG GT brake noise issue.

Cause

The root cause of the Mercedes-Benz AMG GT brake noise is identified as frictional vibrations within the brake system. AMG brake systems are designed for high loads, which can sometimes lead to these noises under specific operating conditions and driving styles. Factors like speed, brake pressure, and ambient conditions (temperature, air humidity) can influence their occurrence.

Important Warnings

Technicians performing this repair must observe a critical warning:

• "IMPORTANT: Be absolutely certain to not allow paste between friction surfaces of the pad and disc!" This prevents critical safety issues and ensures proper brake function.

Diagnosis

To accurately diagnose the Mercedes-Benz AMG GT brake noise, technicians follow a structured process:

1. Initial Checks: The technician will first check for any other relevant documents for the specific model series. They will attempt to reproduce the complaint and identify which axle (front or rear) and side the noises originate from, ideally during a test drive with the customer.
2. Component Inspection: The affected brake system components are inspected for wear, mechanical damage, or localized overheating damage. Any damaged components must be replaced before re-assessing the noise.
3. Lift Inspection: With the vehicle secured on a lift, the engine is started, and the brake pedal is depressed 3-4 times. Each wheel is then checked manually to ensure it turns freely. If a wheel does not turn freely, this underlying issue must be resolved first.
4. Rotor and Pad Assessment: The condition of the brake rotors and pads is assessed visually and according to Workshop Information System (WIS) guidelines, looking for signs of stagnation or other issues.

Repair Procedure Summary

The repair procedure varies slightly depending on whether the noise originates from the front or rear axle.

For Front Axle Noise:

1. Remove the front axle brake linings.
2. Clean all contact points on the brake lining, brake caliper, and carrier.
3. Clean the bonding surface where pistons contact the back of the brake pad. Apply adhesive film to the backplate of the piston-side brake lining. For 6-piston calipers, apply only in the center piston area. For other caliper configurations, apply where the piston(s) makes contact with the back of the pad.
4. After installing the brake linings, actuate the brake for 30 seconds.

For Rear Axle Noise:

1. Remove the rear axle brake pads.
2. Clean all contact points on the brake lining, brake caliper, and carrier.
3. Grease the contact points (specifically the red areas shown in the attachment) between the brake lining and the guide of the brake caliper with heat-resistant lubricating paste.
4. Clean the bonding surface where pistons contact the back of the brake pad. Apply adhesive film to the backplate of the piston-side brake lining.

Required Tools or Parts

Specific parts are required for this repair:

• 3M F9469PC: Alternate Adhesive Transfer Tape (Quantity 1)
• A001 989 87 51: Heat-resistant lubricating paste (Quantity <1)
• A 190 423 32 00: Adhesive Transfer Tape (Quantity 1, may need modification to fit or an alternate can be used)

Brake Bedding Process

After the repair, a specific brake bedding process is crucial to ensure optimal performance and reassess the Mercedes-Benz AMG GT brake noise:

1. Customer Mileage Clarification: Before the trip, the customer should be informed that approximately 30 miles will be incurred.
2. Route Selection: Choose a suitable route where speeds of approximately 65 MPH can be achieved.
3. Braking Cycles: Brake the vehicle 15 times from 62 MPH down to 30 MPH, using a brake pressure of approximately 30 bar (which can be read out using XENTRY). Crucially, avoid emergency stops and braking within the ESP control range. Maintain a cooling distance of about 1 mile between each brake application.
4. Final Cooling: Drive approximately 3 miles to allow the brake system to cool down.
5. Reassessment: After this process, the noise should be reassessed.

Owner Action

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

---

Source: NHTSA ID 11012904