GENERAL MOTORS
DCS6978
URGENT - DISTRIBUTE IMMEDIATELY
Date:

August 14, 2024

Subject: N232430450 - Service Update
Possible Engine Coolant Contamination
Models: 2024 Chevrolet Silverado 2500HD/3500HD
2024 GMC Sierra 2500HD/3500 HD
Equipped with 6.6L Diesel Engine (RPO L5P)

General Motors is releasing Service Update N232430450 today.
What Should Dealers Do: Dealers should review IVH or the Dealer Maxis reports
for open VINs in their inventory. Dealers can view the attached bulletin and it
will also be displayed in Service Information tomorrow.
A Stock VIN list is not included as our records show there are no vehicles in
dealer new inventory.

END OF MESSAGE

Service Update
N232430450 Possible Engine Coolant Contamination
Release Date:
Attention:

August 2024

Revision:

00

This service update includes vehicles in dealer inventory and customer vehicles that return to the
dealership for any reason. This bulletin will expire at the end of the involved vehicle’s New Vehicle Limited
Warranty period.

Make
Chevrolet

Model
Silverado 2500HD/3500HD

GMC

Sierra 2500HD/3500HD

Model Year
From
To

RPO

2024

L5P

2024

Description
ENGINE-DIESEL, 8 CYL, 6.6L,
DI, V8, TURBO, DURAMAX,
GEN 5, VAR. 1

Involved vehicles are marked “Open” on the Investigate Vehicle History screen in GM Global Warranty Management
system. This site should always be checked to confirm vehicle involvement prior to beginning any required inspections
and/or repairs.
Condition

Correction

On certain 2024 model year Chevrolet Silverado 2500HD/3500HD and GMC Sierra 2500HD/3500HD
vehicles, equipped with a 6.6L diesel engine (RPO L5P), the engine coolant may have become
contaminated.
Dealers are to inspect the radiator surge tank. If contamination is visible, dealers are to order the required
parts and schedule the customer for another appointment to perform the repair.

Parts
Quantity
6

Part Name

Part No.
12346290 USA
10953464 CAN
19435229 USA
19435229 CAN
86771839
85119145
85119164
85122989
85119169
85584374
85119168
85119162
12695930

Coolant

1

Coolant Flush (Detergent)

1
1
1
1
1
1
1
1
1

Surge Tank
Heater Outlet Hose
Heater Inlet Hose
Radiator Inlet Hose
Radiator Outlet Hose
Radiator Surge Tank Inlet Hose
Radiator Surge Tank Outlet Hose
Engine Coolant Air Bleed Hose
Engine Coolant Air Bleed Pipe

Due to the small number of vehicles involved and due to limited initial parts availability, dealers are encouraged not to
order service parts for use as shelf stock. Parts should only be ordered when inspection determines that it is necessary
to flush the coolant system and replace the hoses.
Reminder: Parts may be removed from SPRINT and Retail Inventory Management (RIM) and be non-returnable. Dealers
should review the affected parts to confirm RIM managed status. Parts may have quantity limiters in effect.
Warranty Information
Labor
Operation
9107312
9107313

Description
Inspect only
Coolant Flush Procedure + Coolant System Parts Replacement

Copyright 2024 General Motors. All Rights Reserved.

Labor
Time
0.2
11.0

Trans.
Type

Net
Item

ZFAT

N/A

Page 1 of 4

Service Update
N232430450 Possible Engine Coolant Contamination
Service Procedure

6595860

1.

Open the hood and inspect the vehicle’s radiator surge tank to determine if it has a contaminated coolant system.
Contamination will be visible as in the picture above, with a film of oily black substance floating on top of the coolant.
•

If there is no contamination visible on top of the coolant, no further action is required. You may close the field
action.

•

If there is contamination visible on top of the coolant, order the parts required to complete the repair and
schedule the customer for another appointment to perform the procedure. When the customer arrives, proceed
to the “Flushing and Repair” section of the repair procedure below.

Flushing and Repair
1.
2.

Remove the RF Wheel Liner. Refer to Front Fender Insulator Replacement in SI.
Disconnect the lower radiator hose from the radiator and allow coolant to drain. Also open the petcock and allow
coolant to drain from each until it has slowed to a drip.
3. Close the petcock and reconnect the lower radiator hose to the radiator.
4. Pull vacuum on the coolant system using Vac-n-Fill Tool (minimum of 20” Hg) and slowly release the vacuum.
5. Disconnect the lower radiator hose and allow coolant to drain as above, then reattach after it is finished draining.
6. Repeat steps 4-5 three times. On the third time, open the petcock again and allow the coolant to drain from there
as well. Close the petcock and reattach the lower radiator hose when finished.
7. Using the Vac-n-Fill tool, pull a vacuum on the coolant system and fill it with fresh water (it may be necessary to do
this a few times until it stops taking water in). Run the engine for one minute.
8. Repeat steps 4-5 three times. On the third time, open the petcock again and allow the coolant to drain from there
as well. Close the petcock and reattach the lower radiator hose when finished.
9. Using the Vac-N-Fill tool, pull a vacuum on the coolant system and fill it with fresh water (it may be necessary to do
this a few times until it stops taking water in). Run the engine for one minute.
10. Repeat steps 4-5 three times. On the third time, open the petcock again and allow the coolant to drain from there
as well. Close the petcock and reattach the lower radiator hose when finished.
11. Add 64oz of cooling system detergent to the surge tank.
12. Pull a vacuum on the cooling system (25” Hg minimum this time) and fill the remaining volume in the cooling
system with fresh water using the Vac-N-Fill tool.
13. Reinstall and tighten the surge tank cap.
14. Run engine at 1,500 RPM until the coolant temperature is 185 degrees Fahrenheit.
15. After the coolant temperature has hit 185 degrees, continue to run engine at 1,500 RPM for 15 minutes, then idle
the engine for 2 minutes before shutting the vehicle off.
Important: Detergent must be flushed out of the cooling system with the engine and coolant still warm, but not hot.
16. Allow the engine to cool for approximately 1 hour, or until squeezing the upper radiator hose determines pressure
has dropped in the coolant system and the coolant in the system is warm but not hot.
17. Remove the lower radiator hose and open the petcock on the radiator.
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Service Update
N232430450 Possible Engine Coolant Contamination
18. As coolant is draining, apply shop air to the surge tank using the Vac-n-Fill tool and attachments to push out as
much detergent as possible from the vehicle’s cooling system.
19. Reconnect the lower radiator hose and close the radiator petcock.
20. Using the Vac-N-Fill tool, pull a minimum of 20” Hg on the coolant system and slowly release the vacuum.
21. Remove the lower radiator hose, allow to drain, and reattach the lower radiator hose.
22. Repeat steps 20-21 three times. On the third time, open the petcock and drain any additional fluid from the
radiator, then close the petcock and reattach the lower radiator hose.
23. Using the Vac-n-Fill tool, pull a vacuum on the coolant system and fill it with fresh water (it may be necessary to do
this a few times until it stops taking water in). Run the engine for one minute.
24. Remove the lower radiator hose, allow to drain, and reattach the lower radiator hose.
25. Using the Vac-N-Fill tool, pull a minimum of 20” Hg on the coolant system and slowly release the vacuum.
26. Remove the lower radiator hose, allow to drain, and reattach the lower radiator hose.
27. Repeat steps 20-21 three times. On the third time, open the petcock and drain any additional fluid from the
radiator, then close the petcock and reattach the lower radiator hose.
28. Using the Vac-n-Fill tool, pull a vacuum on the coolant system and fill it with fresh water (it may be necessary to do
this a few times until it stops taking water in). Run the engine for one minute.
29. Remove the lower radiator hose, allow to drain, and reattach the lower radiator hose.
30. Using the Vac-N-Fill tool, pull a minimum of 20” Hg on the coolant system and slowly release the vacuum.
31. Remove the lower radiator hose, allow to drain, and reattach the lower radiator hose.
32. Repeat steps 20-21 three times. On the third time, open the petcock and drain any additional fluid from the
radiator, then close the petcock and reattach the lower radiator hose.
33. Using the Vac-n-Fill tool, pull a vacuum on the coolant system and fill it with fresh water (it may be necessary to do
this a few times until it stops taking water in). Run the engine for one minute.
34. Remove the lower radiator hose, allow to drain, and reattach the lower radiator hose.
35. Using the Vac-N-Fill tool, pull a minimum of 20” Hg on the coolant system and slowly release the vacuum.
36. Remove the lower radiator hose, allow to drain, and reattach the lower radiator hose.
37. Repeat steps 20-21 three times. On the third time, open the petcock and drain any additional fluid from the
radiator, then close the petcock and reattach the lower radiator hose.
38. Using the Vac-n-Fill tool, pull a vacuum on the coolant system and fill it with fresh water (it may be necessary to do
this a few times until it stops taking water in). Run the engine for one minute.
39. Remove the lower radiator hose, allow to drain, and reattach the lower radiator hose.
40. Using the Vac-N-Fill tool, pull a minimum of 20” Hg on the coolant system and slowly release the vacuum.
41. Remove the lower radiator hose, allow to drain, and reattach the lower radiator hose.
42. Repeat steps 20-21 three times. On the third time, open the petcock and drain any additional fluid from the
radiator, then close the petcock and reattach the lower radiator hose.
43. Using the Vac-n-Fill tool, pull a vacuum on the coolant system and fill it with fresh water (it may be necessary to do
this a few times until it stops taking water in). Run the engine for two minutes.
44. Remove the lower radiator hose, allow to drain, and reattach the lower radiator hose.
45. Using the Vac-N-Fill tool, pull a minimum of 20” Hg on the coolant system and slowly release the vacuum.
46. Remove the lower radiator hose, allow to drain, and reattach the lower radiator hose.
47. Repeat steps 20-21 three times. On the third time, open the petcock and drain any additional fluid from the
radiator, then close the petcock and reattach the lower radiator hose.
48. Replace the following components. Refer to the individual component in SI for replacement instructions.
• Radiator Surge Tank
• Radiator Outlet Hose
• Radiator Inlet Hose
• Heater Outlet Hose
• Heater Inlet Hose
• Engine Coolant Air Bleed Pipe
• Engine Coolant Air Bleed Hose
49. Refill the coolant system. Refer to Cooling System Draining and Filling (GE 47716, L5P) in SI.
Dealer Responsibility
Whenever a vehicle subject to this service update enters your vehicle inventory or is in your facility for service in the
future, and the vehicle is still covered under the New Vehicle Limited Warranty, you must take the steps necessary to be
sure the service update correction has been made before selling or releasing the vehicle.
All new, used, GM Certified Pre-Owned (CPO), courtesy transportation vehicles, dealer shuttle vehicles, CarBravo, etc.
in dealers' possession and subject to this field action must be held and inspected/repaired per the service procedure of
this bulletin before customers take possession of these vehicles. Involved vehicles must be held and not delivered to
customers, dealer-traded, released to auction, used for demonstration, or any other purpose.
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Service Update
N232430450 Possible Engine Coolant Contamination
All GM Certified Pre-Owned (CPO) vehicles currently in the dealers’ inventory within the SHIFT Digital system will be
de-certified and must be held and remedied per the service procedure in this bulletin. Upon submitting an accepted/paid
warranty transaction in the Global Warranty Management (GWM) system, the vehicle can be re-certified for sale within
the SHIFT Digital system, or once again be used in the Courtesy Transportation Program.
Dealer Reports – For USA & Export
The Inventory tab of the Open Vehicle Report will contain Service Update Bulletin VINs that apply to this field action.
This information is intended to assist dealers with the PROMPT COMPLETION of these vehicles. The Customer InService tab will not contain Service Update Bulletin VIN data because the intent of a Service Update Bulletin is to not
inconvenience a customer with a special trip for service. Service Update Bulletins are to be completed when the
customer is in for a regularly scheduled visit.

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 tools, equipment, 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 dealer for information on whether your
vehicle may benefit from the information.

We Support
Voluntary Technician
Certification
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