Cooling - Cold Start Fan Noise
BULLETIN NUMBER: 92-66-56ASECTION: 6B Engine Cooling
NUMBER: 2
CORPORATE REFERENCE NUMBER: 1662O3R
DATE: May 1993
SUBJECT:
COLD START FAN NOISE (INSTALL REVISED "QUICK DUMP" FAN CLUTCH)
MODELS:
1987-92 M-VANS WITH 4.3L ENGINE
1990-92 L-VANS WITH 4.3L ENGINE
1988-92 S/T TRUCKS WITH 4.3L ENGINE
THIS BULLETIN CANCELS AND REPLACES GMC TRUCK BULLETIN 92-6B-56. IT IS BEING REVISED TO INCLUDE M/L VANS, AND TO SERVICE PARTS INFORMATION AND RPO DEFINITIONS. ALL COPIES OF 92-6B-56 SHOULD BE DISCARDED.
CONDITION
Some owners of 1987-92 M-vans, 1990-92 L-vans, and 1988-92 S/T vehicles with a 4.3L engine (RPO LB4, LU2, or L35) and air conditioning (RPO C60) may experience higher than normal fan noise upon cold start up (usually fan noise extended beyond 90 seconds after start up).
CAUSE
This condition may be due to an extended engagement of the fan clutch.
CORRECTION
The condition may be corrected by installing a revised fan clutch which reduces the fan clutch engagement cycle. Vehicles built after the following VIN breakpoints have the new fan clutch installed in production:
Plant VIN
Moraine N2514836
Shreveport N8512403
Pontiac West N0508347
Baltimore NB534465
SERVICE PROCEDURE
Refer to section 6B1 "FAN CLUTCH REPLACEMENT" in the appropriate Service Manual for removal and installation of the fan clutch.
Figure 1 - Typical Fan Assembly:
Important
To maintain a balanced fan assembly, align the yellow paint mark on the fan clutch with the yellow paint mark on the water pump hub (Figure 1.)
SERVICE PARTS INFORMATION
RPO DEFINITIONS:
C60 - AIR CONDITIONER, FRONT, MANUAL CONTROLS
C41 - HEATER, OUTSIDE AIR W/FAN AND DEFROSTER
C42 - HEATER, DELUXE
GU2 - AXLE REAR 2.73 RATIO
GU4 - AXLE REAR 3.08 RATIO
GU5 - AXLE REAR 3.23 RATIO
GU6 - AXLE REAR 3.42 RATIO
GT4 - AXLE REAR 3.73 RATIO
K01 - FAN CLUTCH DRIVE
L84 - ENGINE, 4.3L, (4.3Z) V6
LU2 - ENGINE, 4.3B, (4.3B) V6 HI-OUTPUT TBI
L35 - ENGINE, 4.3L, (4.3W) CENTRAL PORT INJECTION V6 90 DEG
WARRANTY INFORMATION
For vehicles repaired under warranty, use:
Labor Op: J3390
Labor Time: See Applicable Labor Time Guide