Bulletin No.:

Service Bulletin

Date:

18-NA-073
January, 2021

INFORMATION
Subject:

Repair Guidelines for Engine Component Wear

Brand:

Model:

GM Passenger Cars and
Trucks

Model Year:

VIN:

from

to

from

to

2015

2021

All

All

Engine:

Transmission:

All

—

Involved Region or Country

North America, Europe, Russia, Uzbekistan, Middle East, Iraq, Israel, Palestine,
Argentina, Brazil, Bolivia, Chile, Colombia, Ecuador, Paraguay, Peru, Uruguay,
Venezuela, Japan, Cadillac Korea (South Korea), GM Korea Company, China, Taiwan,
Thailand, Singapore, Philippines, Australia, New Zealand, Egypt, Other Africa, South
Africa

Condition

Whenever engines have been disassembled, technicians may encounter some visible
engine wear characteristics on critical engine components. Some technicians may be
replacing engines instead of repairing and replacing worn components as needed.

Cause

These conditions may be caused by the vehicle duty cycle, dust in the environment the
vehicle is being operated in and local fuel quality. In some instances, service personnel
may be improperly diagnosing normal engine wear.

Correction

Review the following graphic examples and information in this bulletin.

Information
The purpose of this bulletin is to assist the service
personnel with graphics and information to use as
guidelines in order to perform the necessary engine
repairs and prevent unnecessary engine replacement.
Important: Prior to component replacement: Refer to
SI to diagnose and identify the root cause of the original
failure. In cases involving suspected bearing failure,
remove and inspect the oil filter. Refer to the Oil Filter –
Inspect for Excessive Debris section in this bulletin.
Important: Prior to completing repairs, do a cost
analysis; in some instances, an engine replacement
may be considered.
Important: If SI diagnosis leads to an inspection of the
cylinder bores and reveals cylinder wall damage (i.e.
excessive scoring or out-of-round), an engine
replacement may be required. Refer to the Cylinder
Bore section in this bulletin (additional reference:
PIP5163D).

Camshaft
Review the following:

4994025

Example of minor scratching/scoring visible on
camshaft lobes and/or camshaft bearing journals. In
this example, the scored components can be replaced
without need for engine assembly replacement.

Copyright 2021 General Motors LLC. All Rights Reserved.

Page 2

January, 2021

Camshaft Bearing Caps
Review the following:

Bulletin No.: 18-NA-073

Connecting Rod End Caps and Bearings
Review the following:

4991477

Example of minor scratching/scoring visible on
camshaft bearing caps. In this example, the scored
components can be replaced without need for engine
assembly replacement.

4992132

Example of minor scratching/scoring visible on
connecting rod bearings. In this example, the scored
components can be replaced without need for engine
assembly replacement.
Crankshaft in Crankcase
Review the following:

Bulletin No.: 18-NA-073

January, 2021

Page 3

4990880

Example of minor scratching/scoring visible on
crankshaft. In this example, the scored components
can be replaced without need for engine assembly
replacement.
Crankshaft Main Bearings and Journal
Review the following:

4986379

Example of minor scratching/scoring visible on
crankshaft. In this example, the scored components
can be replaced without need for engine assembly
replacement.
4985936

Page 4

January, 2021

Bulletin No.: 18-NA-073

Crankshaft, Reluctor Ring and Journal
Review the following:

4986393

4992739

Example of minor scratching/scoring visible on cylinder
wall. In this example, if you cannot catch a toothpick or
fingernail on the scratch, the cylinder bore / engine
block does not require replacement. If the piston is
slightly scored, the scored piston can be replaced
without need for engine assembly replacement
(additional reference: PIP5163D).
Cylinder Bore Honing Marks
Review the following:
4990640

Example of minor scratching/scoring visible on
crankshaft. In this example, the scored components
can be replaced without need for engine assembly
replacement.
Cylinder Bore
Review the following:

4993413

Bulletin No.: 18-NA-073

January, 2021

Page 5

Example of minor scratching/scoring visible on piston.
In this example, inspect for broken and/or stuck rings
and piston ring lands and cylinder wall for damage. If no
cylinder wall damage or other significant damage,
components can be replaced without requiring an
engine assembly replacement.

Oil Filter — Inspect for Excessive
Debris
In cases involving suspected bearing failure, remove
and inspect the oil filter for excessive debris and
damaged pleats. Use the inspection as an indicator of
the amount of material that is displaced through the
engine and lubrication circuits. This may help to avoid
unnecessary engine removal.
Review the following:

4993544

Some technicians may be replacing entire engine
assemblies due to marks found at the top of the
cylinder bore. These marks are considered normal and
are left as a result of a manufacturing laser honing
process. DO NOT replace the cylinder block or the
engine for these normal laser honing marks (refer to
PI0725B).
Piston
Review the following:

4994104

4992916

Page 6

January, 2021

Bulletin No.: 18-NA-073

4994257

4994408

Shown are oil filter pleats with visible metal particles.
In this example, minimal amounts of metal particles are
visible on oil filter pleats and should not pose a
concern.
If excessive amounts of metal particles are observed,
or if there is evidence of damaged oil filter pleats, then
unfiltered oil with bearing debris may have been
pumped into the oil lubrication galleries throughout the
engine. This will require further inspection to confirm
the degree of contamination and appropriate repair
direction. Refer to Service Bulletin 19-NA-256 for HFV6
Gen 1 and Gen 2.

Version Information
Version

3

Modified

Released March 07, 2018
February 07, 2020 – Added the 2020 Model Year, updated the Involved Region or
Country section, updated some PI references and changed the bulletin reference in the
Oil Filter – Inspect for Excessive Debris section.
January 22, 2021 – Added the 2021 Model Year and updated Involved Region or Country
section.

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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