BRAKE PULSATIONS DUE TO UNEVEN OR RUSTY ROTOR/BRAKE DRUM

VEHICLES AFFECTED: All Models

Brake pulsations are normally the result of uneven rotor thickness or an out of round condition in a brake drum. Pulsations can also be caused by a rust build up on the rotor. Under certain conditions, the exterior of the rotor may rust. This would normally not occur unless the vehicle was parked for a few days and corrosive conditions were present. If the rotor exterior does rust, the area under the brake pads usually remains rust free. The difference in friction between the rusted and unrusted areas can cause pulsation for several stops but will improve as the linings scrub the rust off the rotor. Normally two or three stops will return the system to normal. Under adverse rust conditions, as many as five or six stops may be required. Usually this condition will correct itself. It is, however, important that the customer understand what is happening should you receive a comment of this condition.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.