Cooling System - Excessive Fan Noise
87chevy19Number: 88-71-6B
Section: 6B
Date: November, 1987
SUBJECT: EXCESSIVE FAN NOISE
MODELS: 1987 S/T MODELS EQUIPPED WITH 2.8L (VIN CODE R) ENGINES AND AIR CONDITIONING AND 1987-88 C/K, R/V, G AND M MODELS WITH 4.3L, 5.0L, AND 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.
FIGURE NO. 1 - S/T TRUCK:
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.
FIGURE NO. 2 - C/K, R/V, M, G MODELS:
^ 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 received from GMSPO 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/V01/V02/A/C 5.7L with GU4/GU6 and KC4/V01/V02/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 received from GMSPO that fall within the date code break points listed above should be returned to the local GMSPO warehouse for credit with an attached copy of this bulletin. Use Labor Operation J3390 when performing these repairs.
Labor Times: S/T - .4 hr.
C/K - .3 hr.
R/V - .3 hr.
G - .4 hr.
M - .5 hr.