Brakes - FNC Brake Rotor Noise/Pulsation
INFORMATIONBulletin No.: 08-05-23-006H
Date: May 15, 2012
Subject: Information on FNC Brake Rotors
Models:
2009-2011 Buick Lucerne Super with 18" Wheels
2011-2013 Buick LaCrosse, Regal
2009-2011 Cadillac DTS
2013 Cadillac ATS, XTS
2011-2013 Chevrolet Impala, Malibu, Volt
Attention:
If a customer brings their vehicle in with a concern of brake noise or pulsation related to brake pads/rotors, follow the diagnostic procedure below.
Supercede:
This bulletin is being revised to update the models. Please discard Corporate Bulletin Number 08-05-23-006G (Section 05 - Brakes).
Ferritic Nitro-Carburizing (FNC) Technology
Beginning with some models, GM has introduced a new brake rotor technology called Ferritic Nitro-Carburizing (FNC). Simply put, it is an additional step in the manufacturing process of the brake rotor that creates a hardened outer layer on the surface of the rotor. This hardened outer layer reduces the rotor rusting (corrosion) and it also allows the rotor to wear slower. Because this new technology protects against excessive rotor corrosion, it not only aesthetically looks better through open spoke type wheels, it helps reduce thickness variation, which creates pulsation specifically due to "lot rot" corrosion (while the vehicle sits on the dealer's lot between build delivery and customer delivery).
Diagnostic Procedure - Brake Noise/Pulsation Concerns
1. Describe the customer's concern on the Repair Order (i.e. squeak, squeal, growl, pulsation, vibration, shudder, etc.).
2. Can the noise/pulsation be heard/felt (duplicated) while the vehicle is moving with the brake pedal applied?
- Yes - proceed to Step 3.
- No - this concern is not caused by the brake rotor or pad. Do not proceed with this bulletin. Refer to SI for diagnosis and repair.
3. If the concern is noise, proceed to Step 4.
If the concern is pulsation, can the concern be felt through the steering wheel or pedal? Use the parking brake to determine whether this is a front or rear brake rotor issue. Describe/document on the Repair Order what is being felt and at what speed (with brake apply) and if it is a front or rear issue.
4. Perform a visual inspection of the brake rotor(s) and pads. Describe on the repair order (R.O) any unusual wear or corrosion.
- If the brake pads are NOT worn, proceed with Step 5.
- If the brake pads are unevenly worn side to side and/or inner to outer, determine cause, correction and describe on repair order, proceed with Step 7.
5. Burnish the brakes by performing 10-15 moderate stops from 56-64 km/h (35-40 mph) with cooling time between stops. Did this correct the customer's concern?
- Yes - no further action is required.
- No - proceed to Step 6.
6. If the customer's concern is noise related, proceed with Step 7. If the customer's concern is pulsation related, proceed with Step 8.
7. Replace the brake pads. Did this correct the customer's concern?
- Yes - no further action is required. Proceed to Step 9.
- No - proceed to Step 8.
Important
Only clean-up/refinish rotor(s) determined to be the cause of issue (Refer to the "Brake Rotor Clean-up/Refinish Procedure" in the latest version of Corporate Bulletin Number 00-05-22-002).
8. Clean-up/refinish the rotor(s). Before and after refinish, rotor thickness measurements must be documented on the repair order. Refer to the latest version of the "Brake Rotor Clean-Up/Refinish Procedure" in Corporate Bulletin Number 00-05-22-002.
9. The following information must be documented on the repair order: detailed condition, cause, correction information and rotor measurements, per the above steps.
Warranty Information
For vehicles repaired under warranty, select the appropriate labor operation based on the repair that corrected the customer's concern:
Important
Labor operation H9709 - Brake Burnish is not a published labor operation and will not be found in the Labor Time Guide. This labor operation should be used to claim the necessary time for cleaning up the braking surfaces for thickness variation pulsation due to "lot rot" corrosion. Refer to Brake Pulsation section of this bulletin for procedure. Thickness Variation Pulsation due to "lot rot" corrosion occurs when vehicles are not driven for an extended period of time. This type of corrosion clean-up is covered under the terms of the new vehicle warranty coverage.
Disclaimer