ENGINE OVERHEAT AT LOW VEHICLE SPEEDS OR DURING EXTENDED IDLE

MODELS: 1985 C/K 2500-3500 WITHL E8(454), H5D HEAVY DUTY EMISSIONS AND ELECTRIC BOOST COOLING FAN

Some 1985 C/K 2500 - 3500 trucks equipped with the 454 engine, H5D heavy duty emissions, and the electric boost cooling fan may experience an engine overheat at an extended idle or low vehicle speed operation (under 5 mph).

This condition may be caused by the electric boost cooling fan running in the reverse direction. If this condition is encountered, test the fan to verify that the airflow is toward the rear of the vehicle through the radiator. If the airflow from the fan is toward the front of the vehicle, this condition can be corrected by reversing the wires in the fan harness connector. See Figure No. 1.

This condition was corrected in production beginning with the following VIN breakpoints.

Flint 501986 St. Louis 503471 505403 Janesville 506052

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.