Coolant Leak, Coolant Consumption and/or Low Coolant Message Being Displayed On the Driver Information Center (DIC) – 2017-2023 Chevrolet Silverado & GMC Sierra

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Copyright 2022 General Motors LLC. All Rights Reserved. Service Bulletin Bulletin No.: 18-NA-098 Date: September, 2022 INFORMATION Subject: Diagnostic Tip for Coolant Leak, Coolant Consumption and/or Low Coolant Message Being Displayed On the Driver Information Center (DIC) Brand: Model: Model Year: VIN: Engine: Transmission: from to from to Chevrolet Silverado 2017 2018 Equipped with 6.6L Diesel Engine (RPO L5P, L5D) Silverado 2500/3500 2019 2023 Silverado 4500HD, 5500HD and 6500HD 2019 2023 GMC Sierra 2017 2018 Sierra 2500/3500 2019 2023 Involved Region or Country North America, Middle East, Australia, New Zealand. Condition Some customers may comment on a coolant leak, coolant consumption and/or low coolant message being displayed on the driver information center (DIC). Correction Use the illustrations below, that show the areas in blue, to help identify where to look for possible coolant leak paths for the Duramax engine. Page 2 September, 2022 Bulletin No.: 18-NA-098 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. 5027608 1. Plugs in Cylinder Head (PLUG, CYL HD CORE HOLE) (Qty 8) 2. Block Heater (HEATER, ENG COOL) 3. Cup Plugs in Block (PLUG, ENG BLK COOL DRN HOLE (OD=40MM) (Qty 5) 5027641 1. Coolant Hose and Clamp 2. Thermostat Housing (SEAL, ENG COOL THERM (O RING) 3. O-Ring for Bypass Pipe (SEAL, THERM BYPASS PIPE (O RING)) 4. Flange with Gasket for Bypass Pipe (GASKET, THERM BYPASS PIPE) 5. O-Ring Seal (Front Cover to Water Pump) (SEAL, W/PMP CVR) 6. Seal-Water Pump to Pipe (GASKET, W/PMP OTLT PIPE) 7. Coolant Hose and Clamp 8. Cup Plug on Block (PLUG, ENG BLK COOL DRN HOLE) Bulletin No.: 18-NA-098 September, 2022 Page 3 5028324 1. O-Ring (Water Pipe to Oil Cooler) (SEAL, W/PMP OTLT PORT) 2. Either end of the Oil Cooler Adapter (Elbow) (GASKET, ENG OIL CLR ADAP) 3. Seal in the Oil Coolet (GASKET, ENG OIL CLR) Note: Ghost view of the Oil Cooler to reveal O-ring and cover gasket and 2 adapter gaskets (Oil Filter not shown). 5028590 1. Cup Plugs (Qty 2)(One per side in rear of Cylinder Head) (PLUG, CYL HD CORE HOLE) 2. Gaskets under Flange, 1 location on EGR Bypass Valve (Serviced with VALVE, EGR VLV CLR BYPASS) 3. Hose Clamps, 5 locations 4. Turbo Coolant Feed Pipe (GASKET, TURBO COOL FEED & RTN PIPE) 5. Gaskets under Flange, 2 locations on EGR Valve (Service with VALVE, EGR) 6. Cup Plug in Bypass Valve (Service with VALVE, EGR) 7. Cover on Flywheel Housing (GASKET, FLYWHL HSG CVR) Page 4 September, 2022 Bulletin No.: 18-NA-098 5028593 1. Gasket for Turbo coolant pipes (GASKET, TURBO COOL FEED & RTN PIPE) (Qty 2) 2. Ghost view of Upper Intake Manifold and ERG Coolant Pipe. Inlet Adapter removed to reveal EGR Coolant Return Pipe. 3. Hose Clamps for Turbo Coolant Pipes and DEF Coolant Pipe (Qty6) 5028604 Note: A leak on the top of the engine will trail down the back of the engine and appear as a rear cover leak. 1. Hose Clamps on the EGR Coolant Return Hose (Qty 2) 2. O-Ring for EGR Coolant Return Pipe (SEAL, EGR COOL FEED PIPE) (Qty 2) 3. Gaskets under Flanges for EGR Coolant Feed and Return Pipes (SEAL, EGR COOL FEED PIPE) (Qty 2) 5028676 1. Gaskets between Cylinder, Heads and Water Crossover Housing (GASKET, ENG COOL THERM HSG) (Qty 2) 2. Head Gaskets (GASKET, CYL HD) Bulletin No.: 18-NA-098 September, 2022 Page 5 Version 6 Modified Released April 05, 2018 Revised July 25, 2018 – Added the 2019 to Model Year. Revised June 24, 2019 – Added the 2020 Model Year. Revised November 06, 2020 — Added 2021 Model Year and Silverado 4500HD, 5500HD and 6500HD Revised January 11, 2022 – Added 2022 to Model Year. Revised September 09, 2022 – Added 2023 to Model Year. 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. WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

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