Intake Manifold Replacement - Lower

Removal Procedure

Important: This engine uses a sequential multiport fuel injection system. Injector wiring harness connectors must be connected to their appropriate fuel injector or exhaust emissions and engine performance may be seriously affected.






1. Disconnect the battery ground (negative) cable. Refer to Battery Negative Cable Disconnect/Connect Procedure in Starting and Charging.
2. Remove the upper intake manifold. Refer to Intake Manifold Replacement (Upper).
3. Disconnect the radiator inlet hose from the engine. Refer to Radiator Hose Replacement - Inlet in Cooling System.
4. Disconnect the thermostat bypass hose from the thermostat bypass pipe and lower intake manifold pipe.
5. Remove the thermostat bypass pipe.
6. Remove the left (front) valve rocker arm cover. Refer to Valve Rocker Arm Cover Replacement (Left Front).
7. Remove the generator.
8. Remove the right (rear) valve rocker arm cover. Refer to Valve Rocker Arm Cover Replacement (Right Rear).






9. Disconnect the engine coolant temperature (ECT) wiring harness.






10. Disconnect and remove the fuel injector and manifold air pressure (MAP) wiring harness.






11. Remove the fuel pipe clip bolt.






12. Remove the fuel pipe clip.






13. Disconnect the fuel feed pipe from the fuel injector rail. Refer to Fuel Hose/Pipes Replacement (Filter to Engine) in Powertrain Management.






14. Disconnect the fuel return pipe from the fuel injector rail. Refer to Fuel Hose/Pipes Replacement (Filter to Engine) in Powertrain Management.






15. Remove the fuel injector rail. Refer to Fuel Rail Assembly Replacement in Powertrain Management.
16. Remove the power steering pump from the front engine cover and reposition. Refer to Power Steering Pump Replacement in Steering.






17. Disconnect the heater inlet pipe with heater hose from the lower intake manifold and reposition. Refer to Heater Pipe Replacement - Inlet (3.1L) in Heating and Air Conditioning.






18. Remove the lower intake manifold bolts.
19. Remove the lower intake manifold.
20. Remove the valve rocker arms and the push rods. Refer to Valve Rocker Arm and Push Rod Replacement






21. Remove the lower intake manifold gaskets and seals.
22. Clean the lower intake manifold gasket and seal surfaces on the cylinder heads and the engine block.
23. Clean the gasket and seal surfaces on the lower intake manifold with degreaser.
24. Remove all the loose RTV sealer.






25. If replacing the lower intake manifold remove the Engine Coolant Temperature (ECT) sensor. Refer to ECT Sensor Replacement in Powertrain Management.






26. If replacing the lower intake manifold remove the water outlet bolts.
27. Remove the water outlet.






28. If replacing the lower intake manifold remove the thermostat.

Installation Procedure






1. If removed, install the thermostat.






2. If removed, install the water outlet.

Notice: Refer to Fastener Notice in Service Precautions.

3. Install the water outlet bolts.
- Tighten the water outlet bolts to 25 Nm (18 ft. lbs.).






4. If removed, install the Engine Coolant Temperature (ECT) sensor. Refer to ECT Sensor Replacement in Powertrain Management.






5. Apply 8-12 mm (0.08-0.11 inch) bead of RTV Sealer, GM P/N 12345739 or equivalent, on each ridge where front and rear of the lower intake manifold contact the engine block (1).
6. Install the lower intake manifold gaskets.
7. Install the push rods and the valve rocker arms. Refer to Valve Rocker Arm and Push Rod Replacement.






8. Install the lower intake manifold.
9. Apply sealant, GM P/N 12345382 to the threads of the bolts.

Notice: An oil leak may result if the vertical bolts are not tightened before the diagonal bolts.





10. Install NEW lower intake manifold bolts.

Tighten
A. Tighten the lower intake manifold bolts in sequence to 7 Nm (62 in. lbs) on the first pass.
B. Tighten the lower intake manifold bolts (1,2,3,4) in sequence to 13 Nm (115 in. lbs) on the final pass.
C. Tighten the lower intake manifold bolts (5,6,7,8) in sequence to 25 Nm (18 ft. lbs) on the final pass.







11. Connect the heater inlet pipe and heater hose to the lower intake manifold. Refer to Heater Pipe Replacement - Inlet (3.1L) in Heating and Air Conditioning.
12. Install the power steering pump to the front engine cover. Refer to Power Steering Pump Replacement in Steering.






13. Install the fuel injector rail. Refer to Fuel Rail Assembly Replacement in Powertrain Management.






14. Connect the fuel return pipe to the fuel injector rail. Refer to Fuel Hose/Pipes Replacement (Filter to Engine) in Powertrain Management.






15. Connect the fuel feed pipe to the fuel injector rail. Refer to Fuel Hose/Pipes Replacement (Filter to Engine) in Powertrain Management.






16. Install the fuel pipe clip.






16. Install the fuel pipe clip bolt.
- Tighten the fuel pipe clip bolt to 8 Nm (71 inch lbs.).






17. Connect the thermostat bypass hose to the thermostat bypass pipe and lower intake manifold pipe.
18. Connect the radiator inlet hose to the engine. Refer to Radiator Hose Replacement - Inlet in Cooling System.






19. Install and connect the fuel injector and manifold air pressure (MAP) wiring harness.






20. Connect the Engine Coolant Temperature (ECT) wiring harness.
21. Install the right (rear) valve rocker arm cover. Refer to Valve Rocker Arm Cover Replacement (Right Rear).
22. Install the generator.
23. Install the left (front) valve rocker arm cover. Refer to Valve Rocker Arm Cover Replacement (Left Front).
24. Install the upper intake manifold. Refer to Intake Manifold Replacement (Upper).
25. Connect the battery ground (negative) cable. Refer to Battery Negative Cable Disconnect/Connect Procedure in Starting and Charging.