ENGINE OVERHEATS -POSSIBLE INCORRECT THERMOSTAT INSTALLED

MODELS: 1986-1987 LIGHT AND MEDIUM DUTY TRUCKS WITH 7.4L (VIN CODES N AND W) AND 6.OL, 7.OL (VIN CODES B AND E) ENGINES

Some 1986-1987 light and medium duty trucks equipped with 7.4L, 6.OL or 7.OL engines may experience an engine overheat condition. This condition may be caused by the engines being built with the incorrect style thermostat. Ther- mostats are not interchangeable between the 6.OL/7.OL and the 7.4L engines and can be easily identified by their physical differences (See Figure No. 1)

If this condition is encountered, it can be repaired by installing the correct thermostat. Follow the procedures in Section 6B-Engine Cooling of the appropriate service manual. PARTS INFORMATION

QUANTITY ENGINE PART NUMBER REQUIRED ------ ----------- -------- 7.4L 3041390 1 6.OL, 7.OL 3058469 2

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.