Generator Noise at Idle, Slow Speeds (Replace Heater Inlet/Outlet Pipe Assms)

This bulletin is being revised to update model and parts information, repair procedures and labor times. Please discard Corporate Bulletin Number 99-06-03-005 (Section 6 -- Engine/Propulsion System).

This bulletin is being issued to provide additional information regarding the generator noise condition described below. The heater inlet and outlet pipe adapter bolts were implemented into production in March, 1999 in order to reduce the generator noise condition. However, as part of our continuing effort to further reduce the generator noise condition and to ensure a high level of customer satisfaction, new heater inlet and outlet pipe adapters are now available from GMSPO.

In addition, for the 1999 Park Avenue/Ultra ONLY, a new heater inlet hose assembly is also available from GMSPO.

1. Old Style
2. New Style

Some customers may comment about a magnetic whine/noise/hum/moan/vibration that can be heard inside the passenger compartment. This condition may be more pronounced at idle, slow speeds, decelerating and during parking lot maneuvers.

This condition may be caused by the normal magnetic pulses from the generator being transmitted into the passenger compartment by way of the heater inlet and outlet fasteners, adapters and hoses that are attached to the bracket shared by the generator mounting.

For vehicles built BEFORE the following VIN breakpoints that have NOT had Service Bulletin 99-06-03-005 incorporated:

Caution: As long as there is pressure in the cooling system, the temperature can be considerably higher than the boiling temperature of the solution in the radiator without causing the solution to boil. Removal of the heater inlet and/or outlet pipe adapters and/or hoses while the engine is hot and cooling system pressure is high, will cause the solution to boil instantaneously -- possibly with explosive force -- spewing the solution over the engine, fenders and the person removing the adapters and/or hoses. Under certain conditions, the ethylene glycol in the engine coolant could be ignited.

Caution: An electric fan under the hood can start up even when the engine is not running and can injure you. Keep hands, clothing and tools away from any underhood electric fan.

Tools Required

Parts Required

1. Drain the cooling system.

Refer to the Draining and Filling Cooling System procedures in the Engine Cooling sub-section of the Service Manual.




2. Remove the heater inlet and outlet pipe adapter bolts (2 and 5) from the heater inlet and outlet pipe adapters (3 and 4).
3. Remove the heater inlet and outlet pipe adapters (3 and 4) from the engine.
4. Mark the position of the heater pipe adapter bracket on the heater hose.

Remove the heater inlet and outlet pipe adapters (3 and 4) from the heater hoses (1 and 6) using the J 38185, Spring Hose Clamp Pliers.




5. On 1999 Park Avenue/Ultra ONLY:

5.1.	Remove the hose clamp from the heater inlet hose at the heater core using the J 37097-A, Hose Clamp Remover/Installer.

5.2.	Remove the heater inlet hose assembly.

5.3.	Remove the hose clamps from the hose assembly.

6. On 1999 Park Avenue/Ultra ONLY:

6.1.	Transfer the adapter bracket mark from the old hose to the new heater inlet hose assembly, P/N 25699450.

6.2.	Install the hose clamps to the new hose assembly.

6.3.	Install the new hose assembly to the heater core.

6.4.	Install the hose clamp to the heater inlet hose at the heater core using the J 37097-A, Hose Clamp Remover/Installer.




7. Align the bracket of the new heater pipe adapter with the mark on the heater hose.

7.1.	Install the new heater inlet pipe adapter (3), P/N 12569584, and the new heater outlet pipe adapter (4), P/N 12569648, to the heater hoses.

7.2.	Reposition the heater hose clamps using the J 38185, Spring Hose Clamp Pliers.

8. Apply a thin layer of lubricant, such GM Goodwrench® Rubber Lubricant, P/N 12345884 (in Canada, use P/N 5728223), or equivalent to the O-rings of the heater inlet and outlet pipe adapters.
9. Install the heater inlet and outlet pipe adapters (3 and 4) to the engine.

Ensure the pipe adapters are properly seated.

10. Install two new heater inlet and outlet pipe adapter bolts (2 and 5), P/N 11517999.

Important: Do not exceed the specified torque. The isolation bolts are intended to eliminate the hard interface between the generator mounting bracket and the heater inlet and outlet pipe adapters. After tightening the bolts, ensure the hose has movement.

Tighten
Tighten the two new heater inlet and outlet pipe adapter bolts to 10 N·m (89 lb in).

11. Fill the cooling system.

Refer to the Draining and Filling Cooling System procedures in the Engine Cooling sub-section of the Service Manual.

For the following vehicles:

Caution: As long as there is pressure in the cooling system, the temperature can be considerably higher than the boiling temperature of the solution in the radiator without causing the solution to boil. Removal of the heater inlet and/or outlet pipe adapters and/or hoses while the engine is hot and cooling system pressure is high, will cause the solution to boil instantaneously -- possibly with explosive force -- spewing the solution over the engine, fenders and the person removing the adapters and/or hoses. Under certain conditions, the ethylene glycol in the engine coolant could be ignited.

Caution: An electric fan under the hood can start up even when the engine is not running and can injure you. Keep hands, clothing and tools away from any underhood electric fan.

Tools Required

Parts Required

1. Drain the cooling system.

Refer to the Draining and Filling Cooling System procedures in the Engine Cooling sub-section of the Service Manual.




2. Remove the heater inlet and outlet pipe adapter bolts (2 and 5) from the heater inlet and outlet pipe adapters (3 and 4).
3. Remove the heater inlet and outlet pipe adapters (3 and 4) from the engine.
4. Mark the position of the heater pipe adapter bracket on the heater hose.

Remove the heater inlet and outlet pipe adapters (3 and 4) from the heater hoses (1 and 6) using the J 38185, Spring Hose Clamp Pliers.




5. On 1999 Park Avenue/Ultra ONLY:

5.1.	Remove the hose clamp from the heater inlet hose at the heater core using the J 37097-A, Hose Clamp Remover/Installer.

5.2.	Remove the heater inlet hose assembly.

5.3.	Remove the hose clamps from the hose assembly.

6. On 1999 Park Avenue/Ultra ONLY:

6.1.	Transfer the adapter bracket mark from the old hose to the new heater inlet hose assembly, P/N 25699450.

6.2.	Install the hose clamps to the new hose assembly.

6.3.	Install the new hose assembly to the heater core.

6.4.	Install the hose clamp to the heater inlet hose at the heater core using the J 37097-A, Hose Clamp Remover/Installer.




7. Align the bracket of the new heater pipe adapter with the mark on the heater hose.

7.1.	Install the new heater inlet pipe adapter (3), P/N 12569584, and the new heater outlet pipe adapter (4), P/N 12569648, to the heater hoses.

Align the new heater pipe adapter bracket with the mark on the heater hose.

7.2.	Reposition the heater hose clamps using the J 38185, Spring Hose Clamp Pliers.

8. Apply a thin layer of lubricant, such GM Goodwrench® Rubber Lubricant, P/N 12345884 (in Canada, use P/N 5728223), or equivalent to the O-rings of the heater inlet and outlet pipe adapters.
9. Install the heater inlet and outlet pipe adapters (3 and 4) to the engine.

Ensure the pipe adapters are properly seated.

10. Install the two heater inlet and outlet pipe adapter bolts (2 and 5).

Important: Do not exceed the specified torque. The isolation bolts are intended to eliminate the hard interface between the generator mounting bracket and the heater inlet and outlet pipe adapters. After tightening the bolts, ensure the hose has movement.

Tighten
Tighten the two heater inlet and outlet pipe adapter bolts to 10 N·m (89 lb in).

11. Fill the cooling system.

Refer to the Draining and Filling Cooling System procedures in the Engine Cooling sub-section of the Service Manual.

Parts are currently available from GMSPO.

For vehicles repaired under warranty, use: