23-NA-186

Bulletin No.:
Service Bulletin
Date:
23-NA-186
February, 2024
INFORMATION
Subject:
Brand:
Chevrolet
Information on Gas Vacuum Pump Replacement Part Update
Model:
Model Year:
from
to
Medium Duty LCF
3500, 4500
2016
2023
Low Cab Forward
3500 HG, 4500
HG, 5500 HG and
5500 XG
2024
2024
VIN:
from
to
Engine:
Transmission:
6.0L. 6.6L
Involved Region or Country
North America
Information
The vacuum pump service part for affected vehicles listed in this bulletin has been
superseded and is now the same vacuum pump that is the service part for the 6.6L gas
engine. The updated pump requires the outlet vacuum hose to be rerouted for proper
fitment. Follow the service procedure below to install the updated replacement vacuum
pump and reroute the outlet vacuum hose as set forth below.
In order to improve the supply of these parts it has been decided to revert to making
vacuum pumps available individually rather than in kits.
Important: It is essential that the correct pulley for the application is used. Refer to the
Parts Information section.
Important: Service agents must comply with all
International, Federal, State, Provincial, and/or
Local laws applicable to the activities it performs
under this bulletin, including but not limited to
handling, deploying, preparing, classifying,
packaging, marking, labeling, and shipping
dangerous goods. In the event of a conflict between
the procedures set forth in this bulletin and the
laws that apply to your dealership, you must follow
those applicable laws.
Service Procedure
1. Remove the drive belt from the drive pulley. Refer
to Drive Belt Replacement in SI or Accessory Drive
Primary Belt Replacement in SI.
2. Remove the two (2) vacuum hoses (inlet and
outlet) from the vacuum pump.
Note: Zip tie locations for removal may vary according
to model year.
6464937
3. Remove zip ties holding the upper vacuum line
from the vacuum pump back to the curve of the Air
Inlet Duct. (See Figure 1.)
4. Working through the pulley access holes, remove
the three (3) vacuum pump mounting bolts. Save
these bolts for reassembly.
Copyright 2024 General Motors LLC. All Rights Reserved.
Page 2
February, 2024
5. Remove the vacuum pump from the accessory
bracket.
6. Install a new vacuum pump pulley onto the
replacement vacuum pump using special tool
EN-49756 Vacuum Pump Pulley Installer.
Note: Pump damage may occur if proper installation
procedures are not followed.
7. Ensure that the mounting surface of the engine is
clean and free of debris.
8. Install the pump onto the engine and working
through the access holes in the pulley, install the
three mounting bolts.
⇒ Tightening torque: 25 N·m (18 lb·ft)
9. Connect the inlet vacuum line onto the vacuum
pump inlet fitting.
6464949
10. Reroute the outlet vacuum hose along the inlet air
duct, in front of the upper radiator hose, attaching
the line to the hose with two (2) zip ties as shown in
the graphic above. Complete the routing by
connecting the end of the vacuum hose to the
vacuum pump outlet fitting.
11. Install the drive belt on the drive pulley. Refer to
Drive Belt Replacement in SI or Accessory Drive
Primary Belt Replacement in SI.
Bulletin No.: 23-NA-186
Bulletin No.: 23-NA-186
February, 2024
Page 3
Parts Information
Note: Only select the parts that coincide with the repair
performed. Replace the part with the P/N outlined in the
Electronic Parts Catalog (EPC) in accordance with the
vehicle VIN.
Causal Part
Description
Part Number
N/A
PUMP, VAC
97656980
N/A
CLIP, BAND (ZIP TIE)
98250712
Pulley Part Number
Qty
97542180 (6.0L)
1
97657703 (6.6L)
1
—
As Required
Note: If you have a vehicle that has an additional drive belt due to an uplift such as a sweeper application, and therefore does
not have clearance for the tapered design pulley, please contact Partech for part number information.
Version
1
Modified
Released February 20, 2024
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these
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 your GM dealer for information on whether your vehicle may benefit from the
information.
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