COLD ENGINE KNOCK (PISTON SLAP)

SUBJECT: COLD ENGINE KNOCK (PISTON SLAP)

MODELS AFFECTED: 1990-1991 DE VILLES, FLEETWOODS, ELDORADOS, AND SEVILLES WITH 4.5L - VIN 3 AND 4.9L - VIN B ENGINES

This bulletin is being revised to change the part number and add the 1991 model year. This bulletin supersedes Service bulletin T-91-75 which should be discarded.

Some 1990-1991 DeVilles, Fleetwoods, Eldorados, and Sevilles with 4.5L and 4.9L V8 engines may exhibit a light engine knocking sound when first started during cold weather. As the engine warms to operating temperature, the noise becomes quieter and may eventually disappear.

To repair this condition install a new piston/liner assembly, P/N 3534204. This kit has a revised piston skirt contour and a thicker wall cylinder liner. The revised part number should be used to replace only those assemblies exhibiting the noise condition.

Parts are expected to be available on February 3, 1992. In case of limited inventory, parts will be placed on 400 control to waive VIP surcharges. Only verifiable emergency VIP orders will be accepted. SPO will make every effort to obtain parts. However, the part will be shipped premium transportation at dealer's expense, and all other order types will be placed on back order until the 400 control is removed.

For warranty purposes use Labor Operations J1300, J1301, or J1307 as required.

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.