INFO ON NON-FACTORY INSTALLED HYDRAULIC PARKING BRAKE

SUBJECT: NON-FACTORY INSTALLED HYDRAULIC PARKING BRAKES

MODELS: 1991 AND PRIOR TRUCKS WITH HYDRAULIC BRAKES

It has come to our attention that, in certain cases, controls are being added to vehicles in an attempt to use the service brake system for a parking brake. Specifically, valves have been added that provide the ability to hold fluid under pressure in the service brake hydraulic system and cause the service foundation brakes to perform the function of a parking brake.

The entire service brake system used on GMC (division) vehicles meets all applicable Federal requirements and has been designed and tested to assure that all brake components will provide trouble-free operation. Installation of any equipment that results in using what is designed and tested for a service system as a parking brake system (including those that attempt to limit the maximum hydraulic pressure) is not recommended by GMC (division).

Customers contemplating such installations should be advised of this position and should be informed that GMC (division) cannot assume responsibility for any problems that may be traceable to installation of equipment that involved modification of all or part of the service brake system.

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.