GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1999 🢒 Seville 🢒 Engine 🢒 Engine Mechanical - 4.6L 🢒 Intake Manifold Cleaning and Inspection

Cleaning Procedure

    Important: Do not reuse the intake manifold-to-cylinder head sealing gaskets.

  1. Remove and discard the intake manifold-to-cylinder head gaskets.
  2. Remove any remaining gasket and/or gasket material from the following:
    3. • Throttle body
    • Throttle body adapter heater plate
    • Intake manifold
  3. Clean the following intake manifold areas in solvent.
    4. • Intake manifold gasket grooves
    • Intake manifold passages
    • Brake booster hose passage
    • EVAP solenoid passage
    • PCV vacuum hose passages
    • MAP sensor passage
    • Throttle body adapter heater plate

    Caution: Wear safety glasses in order to avoid eye damage.

  4. Dry the intake manifold and throttle body adapter heater plate with compressed air.

Inspection Procedure
  1. Inspect the following:
    2. • The sealing grommet on the MAP sensor for tears or damage
    • The fuel rail mounting tabs for damage
    • The intake manifold vacuum passages for debris or restrictions
    • The composite intake manifold assembly for cracks or damage
    • The areas between the intake runners
    • The gasket sealing surfaces and grooves for cracking or damage
    • The fuel injector bores for excessive scoring or damage
    • The throttle body adapter heater plate for restrictions and/or corrosion
  2. Inspect the following thread bolt inserts for looseness or damaged threads:
    3. • Throttle body
    • EVAP solenoid
    • EGR pipe
  3. Inspect the intake manifold cylinder head deck for warpage.
    4. 3.1. Locate a straight edge across the intake manifold cylinder head deck surface.
    3.2. Insert a feeler gauge between the intake manifold and the straight edge.

    A intake manifold with warpage in excess of 0.5 mm (0.020 in), must be replaced.

  4. Repair or replace the intake manifold as necessary.