NO HEAT AT IDLE OR MINIMIZED HEAT AT ABOVE IDLE SPEEDS

No heat at idle or minimized heat at above idle speeds with the subject engine may be caused by a blocked coolant passage leading to the intake manifold.

If inspection of the related components (thermostat, heater core, etc.) reveal no causes for this condition, correct as follows:

(1) Remove thermostat housing.

(2) Use a drill motor and 3/8" drill bit.

(3) Apply grease to the end of the drill to catch the chips.

(4) At a 30 DEG angle below the horizontal and approximately 10 DEG out from the face of the head, drill through the first wall of casting only (see illustration).

(5) With a magnet, remove the remaining chips.

(6) Install thermostat housing.

Labor Operation Number: T1072

Labor Time .7 hours

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.