Engine - Rap or Diesel Noise During Warm-Up
90buick12 Bulletin 90-6-10Date Oct., '90
Ref. No. 90-183-6
Corp. Ref. No. 006106
SUBJECT: ENGINE "RAP" NOISE DURING WARM-UP DIMINISHES WHEN OPERATING TEMPERATURE IS REACHED - NEW SERVICE PISTON
MODELS AFFECTED: 1989-90 CENTURY AND SKYLARK MODELS WITH 3300 V6 ENGINE
Some owners of 1989-90 Skylarks and Century 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 b'rake master cylinder from the driver's side of the car.
Parts are currently available from GMSPO.