GM Service Manual Online
For 1990-2009 cars only

ENGINE OVERHEATS- POSSIBLE INCORRECT THERMOSTAT INSTALLED

THERE HAVE BEEN REPORTED CASES OF 6.0/7.0/7.4L ENGINE OVERHEATS THAT WERE CAUSED BY HAVING THE WRONG STYLE THERMOSTAT INSTALLED.WHEN INVESTIGATING FOR CAUSE OF ENGINE OVERHEAT, CHECK FOR PROPER STYLE OF THERMOSTAT (SEE ILLUSTRATION). USE APPLICABLE LABOR TIME AND OPERATION NUMBER.

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.