EXCESSIVE COOLING FAN NOISE REPLACE FAN CLUTCH - P/N

VEHICLES AFFECTED: 1987 S/T W/2.8L(VIN CODE R) ENGINES AND AIR ----------------- CONDITIONING AND 87-88 C/K, R/V, M/G MODELS W/4.3L,5.0L,5.7L (VIN CODES Z,H,K) ENGINES

Some 1987 S/T and 1987-88 C/K, R/V, M and G models may experience an excessive fan noise (roaring) condition. This condition will display itself as the same type of noise on all affected light duty trucks, however, depending on specific model, may have a different cause.

* ON S/T TRUCKS - this condition may be caused by the fan clutch remaining in maximum engagement. Under normal operations, maximum fan clutch engagement usually occurs following a cold engine start-up until the internal silicone fluid can be re-distributed and the clutch goes into a normal engagement mode. The fan also goes into maximum engagement during maximum cooling demand conditions.

If a "roaring" noise is encountered, it can be repaired by installing a new design fan clutch, P/N 15602918 (See Figure No.1). The new design fan clutch will also be coded GN on the rear of the clutch housing. use the service procedures in Section 6B-Engine Cooling of the S/T Service Manual.

* ON C/K, R/V, M OR G MODELS - the condition may be caused by fan clutches that have mismachined housings. If this condition is encountered, the fan clutch should be removed and the date code checked (See Figure No. 2). Use the service procedures in Section 6B-Engine Cooling of the appropriate service manual. Fans built between Julian Date codes 07987 (079-March 20, 1987) and 11787 (117 - April 27, 1987) should be replaced. New parts should also have the date codes checked to insure a good part is installed.

PARTS INFORMATION

Part Number Application ------ ----------- 22073412 1987-88 M Van with 4.3L, with A/C without GT4

22073403 1988 C/K with 4.3L with GU2/GU4/GU6 and KC4/VO1/VO2/A/C 5.7L with GU4/GU6 and KC4/VO1/VO2/A/C 1987-88 G Van with 4.3L, 5.0L, 5.7L (Vin Code K) with heavy duty cooling and without GT4

22068662 1988 C/K with 5.0L with GU2/GU4/GU6 without A/C

22049776 1987-88 R/V with 5.0L, 5.7L with A/C, without GT4

New parts that fall within the date code break points listed above should be returned to the local warehouse for credit with an attached copy of this bulletin.

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.