Intake Manifold

This procedure covers removal and replacement of the intake manifold on the 5.9L Cummins diesel engine, including all related components and proper sealing procedures.

Warnings

Tools required

Parts

• Intake manifold gasket × 1 — Use OEM or Fel-Pro MS 96410
• Valve cover gasket (if disturbed) × 1 — Use OEM specification
• Fuel rail O-rings × 1 — Use OEM specification
• Throttle body gasket × 1 — Use OEM specification

Preparation

1. Park vehicle on level ground and allow engine to cool completely (minimum 2 hours)
2. Disconnect both negative and positive battery cables to prevent electrical shorts
3. Remove engine cover if equipped
4. Label all electrical connectors, vacuum lines, and fuel lines with tape for correct reassembly
5. Have a camera or phone ready to photograph routing of wiring and hoses before removal

Procedure

1. 1

   Disconnect Air Intake System
   Loosen clamps on air intake tube from turbocharger to air filter housing. Remove complete air intake assembly including resonator box. Disconnect intake air temperature sensor connector if equipped. Set aside entire assembly to provide working room.
2. 2

   Remove Throttle Linkage and Cables
   On mechanically-governed engines (1994-2002), disconnect throttle cable from throttle lever on injection pump. On 2003-2007 common-rail engines the throttle is electronic (APPS) with no mechanical cable at the pump. Remove cruise control cable if equipped. Unbolt cable bracket from intake manifold. Tag position of any adjustment points before removal for easier reinstallation.
3. 3

   Disconnect Fuel System Components
   On the Cummins the fuel injection system does not mount to the intake manifold and generally does not require disassembly for intake removal. Only disconnect fuel-related components if they physically obstruct manifold removal, and cap any opened lines to prevent contamination.
   ⚠Residual fuel pressure may be present. Have shop rags ready to catch any fuel spray when disconnecting lines.
   Torque spec

   Electrical Connector Bolts7 Nm (5 lb-ft)

   Fuel Rail Bolts12 Nm (9 lb-ft)
4. 4

   Remove Valve Cover
   Valve cover removal is generally not required for intake manifold service on the Cummins. Skip unless a component physically obstructs manifold access.
5. 5

   Disconnect PCV and Breather Systems
   The Cummins uses a crankcase breather/vent tube, not a PCV valve. Disconnect the breather/CDR vent tube if it obstructs the intake, keeping hardware organized for reinstallation.
   Torque spec

   PCV Valve8 Nm (6 lb-ft)
6. 6

   Disconnect Sensors and Electrical
   Disconnect the intake air grid heater electrical connections (standard on this engine) — note these are high-current cables, so ensure battery is disconnected first. Remove any temperature sensors mounted in the intake and unbolt any wiring harness brackets attached to it. Ensure all electrical connections are clear of the manifold removal path.
   Torque spec

   Sensor Mounting Bolts11 Nm (8 lb-ft)
7. 7

   Remove Throttle Body (if applicable)
   The Cummins diesel has no throttle body; skip this step (a throttle body gasket is not required for this engine).
   Torque spec

   Throttle Body Bolts10 Nm (7 lb-ft)
8. 8

   Remove Intake Manifold Mounting Hardware
   Beginning from the outside bolts and working toward center, loosen all intake manifold bolts in a crisscross pattern. Remove all bolts completely and set aside. Check for any hidden brackets, ground straps, or support brackets that may still be attached.
9. 9

   Remove Intake Manifold
   Carefully lift intake manifold straight up and away from cylinder head. If manifold is stuck to gasket, gently tap with rubber mallet or use plastic pry tool at thick sections only. Do not pry on gasket surfaces. Once free, inspect manifold ports for carbon buildup or debris.
   ⚠Manifold is heavy and awkward. Use assistant or support as needed to prevent dropping and damaging gasket surfaces.
10. 10

    Clean Gasket Surfaces
    Remove all old gasket material from cylinder head and intake manifold mating surfaces using plastic scraper or non-metallic brush. Clean surfaces thoroughly with brake cleaner and lint-free shop rags. Inspect for any damage, warping, or deep scratches. Surface must be completely clean and dry before new gasket installation.
    ⚠Do not use wire wheels or aggressive metallic scrapers on aluminum surfaces as this will cause damage and leaks.
    ℹ️Cover open intake ports on cylinder head with clean rags to prevent debris from entering engine.
    Torque spec

    Gasket Surface Bolts20 Nm (15 lb-ft)
11. 11

    Install New Gasket and Position Manifold
    Position new intake manifold gasket on cylinder head, ensuring all bolt holes and ports align correctly. Do not use sealant unless specifically required by gasket manufacturer. Carefully lower intake manifold onto gasket, aligning all ports and bolt holes. Ensure gasket does not shift during installation.
12. 12

    Install and Torque Intake Manifold Bolts
    Install all intake manifold bolts finger-tight, ensuring even pressure on gasket. Following manufacturer's sequence (typically center bolts first, then working outward in crisscross pattern), torque all bolts to specification. Perform final torque pass in same sequence to ensure even clamping force.
    ⚠Over-torquing can crack manifold or strip threads in cylinder head. Under-torquing will cause vacuum leaks and poor engine performance.
    Torque spec

    Intake Manifold Bolt25 Nm (18 lb-ft)
13. 13

    Reinstall Throttle Body and Sensors
    Reinstall all sensors removed earlier, applying anti-seize to threads only if specified. Reconnect all electrical connectors, including the grid heater feed, ensuring they seat securely.
    Torque spec

    Throttle Body Bolts10 Nm (7 lb-ft)

    Sensor Mounting Bolts11 Nm (8 lb-ft)
14. 14

    Reinstall Fuel System
    Reinstall any fuel-related components that were disturbed for access, torquing fittings/lines to specification. Note the Cummins injectors and fuel rail do not mount to the intake manifold.
    Torque spec

    Fuel Rail Bolts12 Nm (9 lb-ft)

    Electrical Connector Bolts7 Nm (5 lb-ft)
15. 15

    Reinstall Valve Cover and Accessories
    Reinstall valve cover with new gasket if it was disturbed, torquing cover bolts in the proper sequence. Reinstall breather/vent tube components. Reconnect throttle linkage and cable brackets where applicable. Install air intake system and tighten all clamps securely.
    Torque spec

    PCV Valve8 Nm (6 lb-ft)

    Sensor Mounting Bolts11 Nm (8 lb-ft)

Reassembly

1. Verify all electrical connectors are fully seated and locked
2. Ensure all vacuum lines and breather hoses are properly connected and routed away from hot components
3. Double-check that no tools or rags were left in engine compartment
4. Reconnect battery cables (positive first, then negative)

Verification

• Turn ignition to ON position without starting engine and check for fuel leaks around fuel rail and injectors
• Start engine and listen for any vacuum leaks or unusual noises from intake area
• Allow engine to reach operating temperature and verify smooth idle with no misfires or hesitation
• Check for any fuel, oil, or exhaust leaks around intake manifold gasket areas
• Test drive vehicle and verify normal throttle response and power delivery
• Recheck intake manifold bolt torque after first heat cycle (20-50 miles) to ensure gasket has seated properly

Related trouble codes on this vehicle

Codes that commonly send this job to the bay — tap one for symptoms, causes, and diagnostic steps.

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