06-06-01-019C

Bulletin No.:
Service Bulletin
Date:
06-06-01-019C
March, 2024
INFORMATION
Subject:
Information on Gradual Coolant Loss Over Time with No Evidence of Leak Found
Models:
2004-2006 Buick Rainier
2001-2006 Cadillac Escalade Models
2001-2006 Chevrolet Avalanche, Blazer, Silverado, Suburban, Tahoe, TrailBlazer
Models
2001-2006 GMC Envoy, Jimmy, Sierra, Yukon Models
2001-2004 Oldsmobile Bravada
1998-2002 Pontiac Firebird
2005-2006 Saab 9-7X
with 4.8L, 5.3L, or 5.7L VORTEC® GEN III, GEN IV V8 Engine (VINs G, V, T, M, B, Z —
RPOs LS1, LR4, LM7, LH6, L33, L59)
This bulletin has been revised to add the 1998-2002 Firebird, engine RPO LS1 and the first
Important statement. Please discard Corporate Bulletin Number 06-06-01-019B.
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.
Some vehicles may experience a gradual coolant loss
over time. A very low percentage of cylinder head(s)
manufactured with an embossed Castech logo may
develop a porosity crack in a very specific area.
Inspect the cylinder head assembly to determine if the
casting was manufactured by Castech. This can be
accomplished by inspecting for their casting logo
located on top of the intake port, under the rocker arm
support rail and in the spring deck cavity portion of the
cylinder head.
Important: If the cylinder head(s) are Not a Castech
casting, follow normal diagnostic procedures in SI to
determine the cause of the coolant loss.
Refer to the following illustrations on how to identify
Castech casting and/or the very specific areas of the
cylinder head(s) for a coolant leak from porosity.
Copyright 2024 General Motors LLC. All Rights Reserved.
1860180
Cylinder head(s) location of the Castech manufacturing
casting logo (1).
Page 2
March, 2024
Bulletin No.: 06-06-01-019C
If the cylinder head(s) is a Castech casting (1), inspect
the area around the five oil drain holes for witness
marks indicating coolant seepage over time (2).
Important: If No evidence of coolant loss is found on
inspection of Castech casting cylinder head(s), follow
normal diagnostic procedures in SI to determine the
cause of the coolant loss.
1860178
Close up view of the cylinder head(s) showing the
Castech manufacturing casting logo (1).
1860181
The crack location can be found in any of the
five-cylinder head(s) oil drains. This can be seen as a
clean or shiny area, on an otherwise stained surface
(1). Pressurizing the cooling system at this time may
reveal coolant, air, or a combination, weeping in the
described area. If inspection reveals evidence of
coolant witness marks (1), replace the entire cylinder
head(s) assembly.
1860179
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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