These suggestions and solutions for technical problems come from service bulletins and other technical information published by Mercedes-Benz, selected and rewritten for independent repair shops.

Anti-Corrosion Coating on New Brake Discs

All models

If you’ve been buying new O.E. rotors from your local Mercedes-Benz dealer’s parts department, you’ve noticed that they’re covered with a flat gray anti-corrosion coating.  It seems that some technicians are worried that this may cause braking problems, and perhaps contaminate the new pads, so they spend time removing the coating with various solvents, mild abrasives, and even steam.

This is an entirely unnecessary waste of time.  True, the old protective coating used over a decade ago (a blue glaze) did need to be eliminated before the rotor was installed, but the present day coating is effectively removed during the first brake application and will not affect the performance of the brakes.

However, you may notice the following conditions immediately after these new discs are installed:

• Braking-related noise during the first few brake applications.
• Parking brake squeal (parking brake not applied) with moving vehicle until the brake shoes are seated.
• Odors related to the first time the brakes are used with substantial force.

These conditions will disappear after applying the brakes several times.  Therefore, a thorough test drive by the technician before delivery to the customer is recommended to avoid unnecessary complaints.

Steering Wheel Twitch During Brake Application

Models 211 and 230, 2003 through 2005

If your customer complains that the steering wheel twitches during slow speed brake applications, replace the hydro-mount, or partially hollow rubber style torque strut bushings with solid rubber bushings. Reference the following WIS documents: AR33.15-P-0160R (torque strut removal/installation) and AR33.15-P-0160-02T (torque strut bushing removal/installation). The originally-equipped torque strut bushings can deform under braking applications, resulting in left or right steering wheel rotation. The solid rubber bushings have more resistance to deformation.

Note: Do not replace the torque strut assemblies.

The steering wheel twitch can usually be maximized during slow-speed repetitive brake applications, such as those encountered during stop-and-go traffic, or when approaching a toll booth. It may occur during brake pedal application and/or release. Since ambient temperature may influence the condition, it is important to check for it when the engine is at normal operating temperature.

Note: It is imperative that the condition be verified on a smooth, flat and level road surface.  Failure to observe the aforementioned conditions may result in needless replacement of the torque strut bushings.

The solid rubber torque strut bushings carry Part Number A211 333 11 14.