ENG. RAP NOISE AT WARM-UP NEW PISTON ASSY. AVAILABLE

SUBJECT: ENGINE RAP NOISE DURING WARM-UP (NEW PISTON ASSEMBLY)

VEHICLES AFFECTED: 1989-1990 "A AND N" MODELS WITH 3300 V6 ENGINE

Some owners of 1989-90 A and N models equipped with 3300 V6 engines may comment on an engine "rap" or "diesel" type noise prior to the engine reaching normal operating temperature. The noise will normally appear after one or two minutes of operation and disappear after ten or fifteen minutes of operation.

A new piston assembly has been released to correct this condition. The part number of the new piston assembly is #24501065. It is recommended that all six pistons be replaced when servicing this condition.

The new piston assembly went into Production after June 15, 1990. The date the engine was built can be found on a sticker on the rear valve cover and can be viewed by looking past the brake master cylinder from the driver's side of the car.

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.