Complaint Noises/ squealing from the service brake in various driving situations and ambient conditions

Bulletin number

LI42.10-P-063502

Component

Service brakes

Summary

Complaint Noises/ squealing from the service brake in various driving situations and ambient conditions. Cause Frictional vibrations Remedy The intent of this document is to reduce or eliminate noise from high performance AMG brakes. AMG brakes are designed for performance under high load and in certain scenarios, can emit noise. Some of the scenarios are: • Driving style • Brake pressure and application style (stop-and-go traffic with consistent low brake pressure “riding brakes” where the brakes cannot cool sufficiently between applications). • Ambient temperatures 1. Beginning Diagnostics: a) Check whether the complaint can be reproduced and at which axle or side the noises occur (ideally together with the customer while driving). b) Check the affected system for component wear, mechanical damage or localized overheating damage. Replace damaged components as necessary. c) Assess condition of brake rotors and pads per WIS and visually (i.e. long periods of stagnation, etc...). d) Clean brake components free of brake dust and debris. d) Secure vehicle on a lift. 1. Start the engine and depress the brake pedal 3-4 times. 2. Check each wheel to see if they turn freely by hand. 3. If a wheel is not turning freely by hand, this needs to be addressed prior to re-assessing the noise concern. e) Check whether, apart from this document, an additional document exists for the specific model in question, and if so, work through it and then continue. 2. Specific Axle Work: NOTE: If the brake pad has a metal backing plate, there is no need to affix the adhesive film. Continue with applying chamfer and brake paste as instructed below. IMPORTANT: Be absolutely certain to not allow paste between friction surfaces of the pad and disc! a) If the noises are coming from the front axle. 1. Remove brake linings of front axle. 2. Clean all contact points on brake lining backing plate, including the brake lining guide pins and brake caliper/carrier. 3. Clean bonding surface (where pistons contact back of brake pad). Apply adhesive film to the backplate of the piston-side brake lining where the piston contacts the pad backing plate. See picture "Adhesive and Paste Application Area". If adhesive is already installed on backing plate, you may gently scrape off and re-apply a new adhesive. In some instances the adhesive may be very carefully removed and Molykote applied instead. 4. Chamfer edges (gently round off sharp leading edges) on brake pads. Some pads have vertical grooves, these can be gently chamfered with a triangular file as well. See picture "Chamfering Technique". 5. Apply Molykote to the sides of the backing plate. See picture "Adhesive and Paste Application Area". 6. After installing the brake linings, actuate the brake for 30 seconds. b) If the noises are coming from the rear axle. 1. Remove brake pads of rear axle. 2. Clean all contact points on brake lining backing plate and brake caliper/carrier. 3. Clean bonding surface (where pistons contact back of brake pad). Apply adhesive film to the backplate of the piston-side brake lining. 4. Chamfer edges (round off sharp leading edges) on brake pads. See picture "Chamfering Technique". 5. Grease contact points (red areas on attachment "Rear Pad Grease Area") between brake lining and guide of brake caliper with Molykote. 3. Brake Bedding Process: a) Before trip, the mileage incurred must be clarified with the customer (approx. 30 miles). b) Select a suitable route so speeds of approximately 65 MPH can be achieved. c) If the vehicle is an AMG P3 Hybrid, switch off recouperation prior to bedding in brakes. d) Brake the vehicle 15 times with a brake pressure of approx. 30 bar (have the passenger read it out using XENTRY) from 62 MPH to 30 MPH (no emergency stops and no braking in the ESP control range). Maintain a cooling distance of approx. 1 mile between brake applications. e) Finally drive approx. 3 miles to allow the system to cool. f) Reassess noise.

Owners of these vehicles have filed 30 complaints in the brakes category.