NHTSA ID Number: 11023481
Manufacturer Communication Number: 23-NA-122
TSB/Document Date: 2025-10-01
Summary
This service bulletin provides a procedure to fix an oil leak from a porous area at the cylinder head and how to fix it so that the engine does not have to be replaced.
Bulletin No.: 23-NA-122
Service Bulletin
Date: May, 2025
TECHNICAL
Subject:
Brand:
Engine Oil Leak
Model:
Model Year:
from
Encore GX
2020
Envista
2024
Trax
2024
Trailblazer (VIN M)
2021
VIN:
to
Engine:
from
2024
—
to
—
1.2L Turbo (RPO
LIH)
Involved Region or Country
North America
Condition
Some customers may comment on oil leak between the engine front cover and
turbocharger heat shield.
—
Cause
This condition may be caused by porosity from the engine block
bolt holes.
Important: Do Not replace the engine for this condition.
Copyright 2025 General Motors. All Rights Reserved.
6373157
Page 2
May, 2025
Bulletin No.: 23-NA-122
6373160
- Oil leaking was found to be coming from porosity between the cylinder head bolt hole
and the engine mount boss, bolt hole.
Correction
Remove the cylinder head bolt to apply Loctite© 565 to a new bolt. Refer to the Service
Procedure.
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
6373158
Note: Camshaft removed for clarity.
1. Remove the exhaust camshaft sprocket and position aside. Refer to Camshaft Exhaust Sprocket Replacement.
Bulletin No.: 23-NA-122
May, 2025
Page 3
6898244
2. Remove both the cylinder head bolts.
6373161
Important: Do Not apply Loctite© to the end of the bolt. Damage to the engine block may occur.
3. Apply 565 Loctite© to a new cylinder head bolt as indicated in the graphic above.
4. Install the bolt into the cylinder head and torque to 14.5 Y (10.7 lb ft). Refer to Fastener Specifications.
5. Install the exhaust camshaft sprocket. Refer to Camshaft Exhaust Sprocket Replacement.
Page 4
May, 2025
Bulletin No.: 23-NA-122
Additional Area of Concern
6898293
Note: Graphic above shows the generator removed for clarity on area effected.
A leak may also be located on the other side of the engine block between cylinder head pinch bolt and the generator
mounting area.
If this is the case, the camshaft does NOT have to come out of the engine. If you remove the cam cover, there is
socket clearance access to the pinch bolt in. It is recommended to use a magnetic socket so you don’t drop the bolt
down into the engine while removing it, but the bolt can be removed, Loctite can be applied, and the bolt can be
retightened to 14.5 Y (10.7 lb ft). Allow cure time before starting the engine again. It is easier than the pinch bolt
on the other side which cannot be accessed without removing the camshaft.
Parts Information
Causal
Part
Description
Part
Number
Qty
N/A
BOLT, CYL HD
11547739
As Required
N/A
CLAMP, EXH
PIPE
55513359
1
N/A
GASKET, CTLTC
CONV
12641115
1
N/A
CLAMP, PCV
VAC HOSE
24585201
2
N/A
PIPE, TURBO
COOL FEED
55487866
1
N/A
GASKET,
TURBO OIL RTN
PIPE
55514397
2
N/A
55487539
1
N/A
55497445
1
N/A
NUT, EXH SYS
INTER
11612078
4
N/A
GASKET,
CM/SHF CVR
55487546
1
Bulletin No.: 23-NA-122
May, 2025
Causal
Part
Description
Part
Number
Qty
N/A
BOLT, CR/SHF
BALR
25194208
1
N/A
COVER, TMG
BELT LWR
55487381
1
N/A
BOLT, CM/SHF
SPKT
55487704
2
N/A
HOSE, PCV VAC
55513554
1
N/A
GASKET, EXH
SYS FRT
13499082
1
N/A
PIPE, TURBO
COOL FEED
55509610
1
N/A
OIL, ENGINE
N/A
Refer to EPC
As Required
N/A
565
1
Page 5
Warranty Information
For vehicles repaired under the Powertrain coverage, use the following labor operation. Reference the Applicable
Warranties section of Investigate Vehicle History (IVH) for coverage information.
Labor
Operation
Description
Labor Time
4089088*
Add Loctite© to Cylinder
Head Bolt
3.6 hrs
*This is a unique Labor Operation for bulletin use only.
Version
2
Modified
Released December 18, 2023
Revised May 09, 2025 - Updated Cylinder Head Bolt Part Number in Warranty
Information 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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TSB/Document ID: 23-NA-122
Replacement Service Bulletin Number:
MFR Communication Date: 2025-05-09
MFR Internal Campaign ID/Software Version:
Communication Type: Service Bulletin/Repair Instructions
NHTSA Components: ENGINE
MFR Component System:
MFR Component Subsystem:
Previous TSB | Next TSB |
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