Note: The intake manifold consists of an upper and lower section. Removal of the upper intake manifold is required for only some jobs (eg fuel injector/spark plug service), while some other jobs require removal of both the upper and lower sections as a unit (for example, cylinder head maintenance). If you need to remove the entire assembly, see the section "Intake manifold assembly" in this section.
Removal procedure
1. Disconnect the cable from the negative terminal of the battery.
2. Remove the decorative engine cover. See "Decorative Engine Cover" in this section.
Caution: When disconnecting the throttle body wiring harness, the following precautions must be taken.
- Do not use any mechanical tools such as a screwdriver to disconnect the harness connector (1) from the throttle body (2).
- When removing the lock (3) of the throttle body wiring connector, be careful not to disconnect it from the connector.
- Do not pull on the connector wires.
3. Remove the lock (3) from the throttle body wiring connector.
4. While pressing the connector lock in the direction indicated by the arrow (4), disconnect the throttle body wiring connector.
5. Disconnect the positive crankcase ventilation hose (1) and the vacuum hose (2) for purging the EGR canister.
6. Remove the bolts (3) securing the pipe bracket between the expansion tank and the water outlet.
7. Remove the bolt (4) securing the bracket of the purge valve of the SUPB adsorber.
8. Disconnect the wiring harness connector from the Intake Manifold Tuning (IMTC) valve.
9. Remove the engine wiring harness connector mounting bracket.
10. Move all parts located near the upper intake manifold away from it.
Caution: After removing the upper intake manifold, plug each of the lower intake tract openings with a lint-free cloth to prevent foreign material from entering the engine.
11. Remove the four long (3) and two short (2) bolts securing the upper intake manifold (1) to the cylinder heads and to the lower intake manifold.
Caution: Do not reuse the gaskets located between the upper and lower intake manifolds.
12. Separate the upper intake manifold from the lower half and then remove it from the engine.
13. Remove and discard the gaskets (4) located between the upper and lower intake manifolds.
14. Remove the IMTC solenoid valve (5) and throttle body assembly (6) if required.
Clear
Caution! Since the intake manifold is made of aluminum alloy, do not use wire brushes or steel scrapers to clean it, as this may damage the sealing surfaces. It is preferable to use wooden or plastic scrapers.
1. Clean the mating surfaces, removing all gasket residue.
2. Clean the manifold with a suitable solvent.
3. Dry the valve timing components with compressed air.
Inspection
1. Inspect the intake manifold for the following faults:
- Damaged sealing or mating surfaces.
- Damaged lower intake manifold gasket.
- Damage or excessive contamination of threaded and through holes.
- Cracks or damage to the intake manifold housing.
2. Place a straight edge (1) across the sealing surface (2) of the upper intake manifold.
3. Using the feeler gauge (3), measure the gap between the manifold and the ruler.
4. If the gap between the sealing surface of the upper manifold and the ruler exceeds the specified maximum warpage, replace the manifold.
- Maximum warpage of the upper manifold: 0.05 mm
5. Place a straight edge (1) across the sealing surface (2) of the lower intake manifold.
6. Using the feeler gauge (3), measure the gap between the manifold and the ruler.
7. If the gap between the sealing surface of the lower manifold and the ruler exceeds the specified maximum warpage, replace the manifold.
- Maximum warpage of the lower manifold: 0.05 mm
Installation procedure
1. Installation should be performed in the reverse order of removal, taking into account the following.
- Only new gaskets need to be installed between the upper and lower manifold.
Caution: Tighten the intake manifold bolts in a circle, starting with the center bolt and moving outward from the center.
2. Install the upper intake manifold.
Tighten
Tighten the upper intake manifold to lower intake manifold and cylinder head bolts to 23 N·m (17 lb-ft).
3. Connect the IMTC connector.
4. Connect the throttle valve connector.
5. Install the bolt (4) for fixing the bracket of the purge valve of the SUPB adsorber.
6. Install the bolts (3) to secure the pipe bracket between the expansion tank and the water outlet.
7. Connect the ECU vacuum hose (2) and the positive crankcase ventilation hose (1) to the upper intake manifold.
8. Install the engine wiring harness connector mounting bracket.
The original article can be found on the resource CHEVYMAN