2021 Mercedes-Benz AMG GT Brake Noise TSB

Mercedes-Benz has released Technical Service Bulletin (TSB) LI42.10-P-063502 to address complaints of "Noises/ squealing from the service brake" in various driving situations and ambient conditions for all AMG model designations equipped with steel or ceramic brakes (code B07).

This TSB, updated on February 3, 2025, with version 9, provides comprehensive diagnostic and repair steps to resolve the Mercedes-Benz AMG GT brake noise.

Symptoms

Owners may experience "Noises/ squealing from the service brake" during different driving scenarios and under varying environmental conditions. This can manifest as general brake noise, squeals, whirring, or howling.

Cause

The primary 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 inherently lead to noises under certain operating conditions and driving styles. Factors such as speed, brake pressure, temperature, and air humidity can influence these vibrations.

Diagnosis

To accurately diagnose the source of the brake noise, technicians should follow a structured approach:

1. Check for other documents: Verify if any other relevant technical documents exist for the specific model series and address them first.
2. Reproduce the complaint: Work with the customer, if possible, to reproduce the brake noise and identify which axle or side the noises originate from.
3. Inspect brake components: Thoroughly check the affected brake system for component wear, mechanical damage, or localized overheating. Replace any damaged components before re-assessing the noise.
4. Check wheel rotation: With the vehicle on a lift, start the engine and depress the brake pedal 3-4 times. Check each wheel to ensure it turns freely by hand. If a wheel does not turn freely, this issue must be resolved first.
5. Assess rotors and pads: Visually inspect the condition of brake rotors and pads, looking for signs of long periods of stagnation or other issues, as per workshop information system (WIS) guidelines.

Repair Procedure Summary

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

Front Axle Work

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

1. Remove the front brake linings.
2. Clean all contact points on the brake lining and brake caliper/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) make contact with the pad.
4. Chamfer the sharp leading edges of the brake pads, as illustrated in the "Chamfered Pads.png" attachment.
5. 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. Remove the rear brake pads.
2. Clean all contact points on the brake lining and brake caliper/carrier.
3. Grease the contact points (red areas) 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.
5. Chamfer the sharp leading edges of the brake pads, as shown in the "Chamfered Pads.png" attachment.

IMPORTANT: Be absolutely certain to not allow paste between friction surfaces of the pad and disc!

Brake Bedding Process

After the axle-specific work, a crucial brake bedding process must be performed:

1. Clarify mileage: Confirm with the customer that approximately 30 miles will be incurred during this process.
2. Select route: Choose a suitable route where speeds of around 65 MPH can be achieved.
3. Braking cycles: Brake the vehicle 15 times from 62 MPH down to 30 MPH, applying approximately 30 bar of brake pressure. Avoid emergency stops and braking within the ESP control range. Maintain a cooling distance of about 1 mile between each brake application.
4. Final cool-down: Drive approximately 3 miles to allow the brake system to cool down completely.
5. Reassess noise: After the bedding process, re-evaluate the vehicle for any remaining brake noise.

Required Tools or Parts

To perform this repair, specific materials are needed:

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

What Owners Should Know

AMG brake systems are engineered for high performance, and some level of noise can be normal under certain conditions. Mercedes-Benz recommends consulting your Operator's Manual for information on brake care and maintenance, including washing the vehicle after heavy use and using approved cleaning agents. If you experience persistent or unusual Mercedes-Benz AMG GT brake noise or squealing, it is best to have your vehicle inspected by a qualified Mercedes-Benz technician.

Source: NHTSA ID 11014412