Odor from Under Hood, Coolant Odor (Flush Cooling System and Replace Coolant Hoses)

This bulletin is being revised to update the part information for the new GM Heavy Duty Cooling System Cleaner in the U.S. and Canada and to alert dealers of an important change to the directions for using the new cooling system cleaner. Please discard Corporate Bulletin Number 04-06-02-010A (Section 06 -- Engine/Propulsion System).

Some customers may comment on an objectionable odor coming from under the hood. It may be found that this odor is from the engine coolant.

Important: This repair is intended for the resolution of odor concern vehicles only. The discoloration of the coolant is normal and not related to odor. It is the result of the sealant pellets that are added to the system during production. DO NOT add sealant pellets when performing this repair.

Flush the cooling system and replace the coolant hoses using the procedure listed below. Clean the cooling system withNew GM Heavy Duty Cooling System Cleaner , P/N 88861344 (in Canada, P/N 88861345). This new cleaner is in liquid form and contains a neutralizer. Do not substitute other cleaners.

Notice: Due to the complexity of these procedures, the following repair steps must be strictly adhered to in order to achieve the intended results. Any deviation or substitution may result in sub-standard cleaning/flushing results or system damage.

Important: Verify the fuel level in the fuel tank. The fuel level should be above ¼ tank before this procedure is started.

Caution: In order to avoid personal injury, do not remove the cap or open the cooling system drains from a hot system. Allow the system to cool first.

1. Drain the cooling system completely and properly dispose of the coolant.

1.1.	Place a container under the radiator drain valve located at the bottom of the left radiator end tank.

1.2.	Using a flat-bladed screwdriver, open the radiator drain valve and allow the coolant to drain from the system.

1.3.	Remove the surge tank cap from the surge tank.

1.4.	Close the radiator drain valve.

1.5.	Raise and properly support the vehicle.

1.6.	Place a container under the left side of the engine. Remove the engine block coolant drain plug and allow the coolant to drain. Install the drain plug.

1.7.	Place a container under the right side of the engine. Remove the engine block heater or plug and allow the coolant to drain. Install the engine block heater or plug.

1.8.	Lower the vehicle.

2. Open the air bleed screw on the water pump tower.
3. Clean the cooling system with New GM Heavy Duty Cooling System Cleaner , P/N 88861344 (in Canada, P/N 88861345). Pour the new cleaner (one-part liquid) into the surge tank. Avoid spilling the solution on the vehicle's finish.
4. Fill the remaining system with plain water. As the system fills, watch for water at the water pump tower. As water begins to seep from the air bleed, close the air bleed screw. If the surge tank fills before the system does, lifting the right side of the vehicle may force the trapped air toward the air bleed.
5. Install the surge tank cap to the surge tank.

Important: To help keep the engine cool and at operating temperature, an industrial cooling fan may be necessary to use in front of the radiator while the engine is being run at fast idle for 40 minutes to one hour.

6. Turn the heater on. Run the engine at fast idle for 40 minutes to one hour.
7. Stop the engine. Allow the engine to cool. Drain the system completely and repeat Steps 1.1 through 1.8.
8. Open the air bleed screw on the water pump tower.
9. Fill the system with plain water. As the system fills, watch for water at the water pump tower. As water begins to seep from the air bleed, close the air bleed screw. If the surge tank fills before the system does, lifting the right side of the vehicle may force the trapped air toward the air bleed.
10. Install the surge tank cap to the surge tank.
11. Run the engine for 10 minutes.
12. Stop the engine. Allow the engine to cool. Drain the system completely and repeat Steps 1.1 through 1.8.
13. Open the air bleed screw on the water pump tower.
14. Fill the system with plain water. As the system fills, watch for water at the water pump tower. As water begins to seep from the air bleed, close the air bleed screw. If the surge tank fills before the system does, lifting the right side of the vehicle may force the trapped air toward the air bleed.
15. Install the surge tank cap to the surge tank.
16. Run the engine for 5 minutes.
17. Stop the engine. Allow the engine to cool. Drain the system completely and repeat Steps 1.1 through 1.8.
18. Remove the surge tank from the vehicle.
19. Remove the battery box from the vehicle. Refer to the Battery Box Replacement procedure in the Engine Electrical sub-section of the Service Manual.
20. Remove the upper and lower (inlet and outlet) radiator hoses from the vehicle.
21. Remove the inlet and outlet heater core hoses from the vehicle.
22. Remove the inlet surge tank vent hose from the vehicle.
23. Install the new inlet surge tank vent hose.
24. Install the new inlet and outlet heater core hoses.
25. Install the new upper and lower (inlet and outlet) radiator hoses.
26. Install the battery box to the vehicle. Refer to the Battery Box Replacement procedure in the Engine Electrical sub-section of the Service Manual.
27. Flush the coolant surge tank thoroughly using hot water to remove any stains.
28. Install the surge tank to the vehicle.
29. Open the air bleed screw on the water pump tower.
30. Refill the cooling system using a 50/70% mixture of clean, drinkable water and use only DEX-COOL® antifreeze. DO NOT use any other type of antifreeze. As the system fills, watch for coolant at the water pump tower. As coolant begins to seep from the air bleed, close the air bleed screw. If the surge tank fills before the system does, lifting the right side of the vehicle may force the trapped air toward the air bleed. The new VAC-N-FILL tool (GE-47716) can also be used to remove trapped air. This tool should only be used for the coolant fill and not for the cooling system cleaner fills (doing so would contaminate the tool).
31. Run the engine and cycle the vehicle from idle to 3,000 RPM in 30 second intervals until the cooling fans come on.
32. Return the engine to idle. Idle for 30 seconds and then turn the engine OFF.
33. Allow the vehicle to cool.
34. Add coolant to the surge tank until the level is approximately 25 mm (1 in) above the top of the Cold Fill Range at the surge tank seam.
35. Install the surge tank cap.

For vehicles repaired under warranty, use: