This procedure covers the removal and replacement of exhaust manifold studs on the 6.7L Cummins diesel engine, including extraction of broken studs and proper installation of new hardware.

Warnings

Tools required

Parts

• Exhaust manifold stud kit (M10 x 1.5) × 1 — Use OEM specification or heavy-duty aftermarket
• Exhaust manifold gasket × 1 — Use OEM specification
• Turbo to manifold gasket × 1 — Use OEM specification
• Exhaust flange nuts × 12 — M10 x 1.5 self-locking nuts
• O2 sensor (if damaged) × 1 — Use OEM specification

Preparation

1. Ensure engine is completely cold to the touch
2. Disconnect both battery cables, negative first
3. Raise and support vehicle on jack stands if accessing lower exhaust components
4. Apply penetrating oil to all exhaust manifold studs and nuts, allow to soak for at least 30 minutes (overnight preferred for seized hardware)
5. Gather all tools and parts before beginning work

Procedure

1. 1

   Remove exhaust components for access
   Disconnect oxygen sensor electrical connector. Using O2 sensor socket, remove oxygen sensor from exhaust manifold or downpipe. Locate and remove exhaust downpipe connection to turbocharger outlet. Remove downpipe hanger bolts to allow exhaust to drop away from manifold.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)

   Hanger Bolts27 Nm (20 lb-ft)
2. 2

   Disconnect turbocharger from manifold
   Remove turbocharger inlet V-band clamp or bolted connection to exhaust manifold. Carefully separate turbocharger from manifold, noting the position of any gaskets or seals. Support turbocharger to prevent damage to oil feed or return lines.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
3. 3

   Remove exhaust manifold heat shield
   Remove all heat shield mounting bolts. Carefully remove heat shield from manifold, noting any clips or retainers. Set aside in clean work area.
   Torque spec

   Heat Shield Bolts10 Nm (7 lb-ft)
4. 4

   Remove exhaust manifold nuts
   Working from the center outward, carefully remove all accessible exhaust manifold nuts from the studs. Use penetrating oil liberally on stubborn nuts. If a nut binds on a damaged stud, carefully cut the nut off with a cutoff wheel or grinder rather than risk breaking the stud. Count all removed nuts to ensure none are left behind.
5. 5

   Remove exhaust manifold
   Carefully lift exhaust manifold away from cylinder head. The manifold may be stuck due to carbon buildup. Gently tap with plastic mallet if necessary. Do not pry between manifold and head to avoid damaging sealing surfaces. Remove and discard old manifold gasket.
   ⚠Manifold may be heavy and awkward to handle. Get assistance if needed to avoid dropping it on engine components.
6. 6

   Assess stud condition and remove intact studs
   Inspect all studs for damage. Mark any broken or damaged studs. For intact studs that need replacement, apply penetrating oil and use stud removal tool or locking pliers to carefully unthread studs from cylinder head. Turn slowly and evenly, backing off if resistance increases significantly.
   ⚠Excessive force can break studs below the head surface, making extraction much more difficult.
7. 7

   Extract broken studs
   For studs broken at or above the cylinder head surface: Use stud removal tool or locking pliers to grip remaining portion. For studs broken below the surface: Center punch the broken stud. Start with a small pilot drill bit (1/8 inch), then progressively larger left-hand drill bits. The reverse rotation may back the stud out. If drilling does not remove the stud, use appropriate size screw extractor. Drill carefully to avoid damaging threads in cylinder head.
   ⚠️Keep drill perpendicular to cylinder head surface. Angled drilling can damage threads or break through into combustion chamber.
   ⚠If extractor breaks off in stud, professional machine shop services may be required.
8. 8

   Clean and inspect cylinder head
   Use wire brush to thoroughly clean all stud holes and manifold mounting surface on cylinder head. Remove all carbon deposits, old gasket material, and debris. Inspect threads in each stud hole for damage. Use M10 x 1.5 thread chaser to clean threads if available. Inspect cylinder head surface for cracks, erosion, or damage. Wipe surface clean with lint-free cloth.
   ℹ️Any cracks or significant damage to cylinder head may require head removal and machine shop repair.
9. 9

   Install new exhaust manifold studs
   Apply a small amount of anti-seize compound to the threads of new studs that thread into the cylinder head (not the nut side). Thread each stud into cylinder head by hand to ensure proper thread engagement. Once all studs are hand-started, use stud installation tool or double-nut method to tighten studs firmly into head. Studs should be snug but manufacturer torque specifications for stud installation vary. Install evenly, checking that all studs protrude equally from the head surface.
   ℹ️Some aftermarket stud kits include specific installation torque values. Follow manufacturer instructions if provided.
10. 10

    Install manifold gasket and manifold
    Position new exhaust manifold gasket onto cylinder head, aligning all ports and stud holes. Carefully position exhaust manifold over studs and onto gasket. Ensure manifold is fully seated against gasket before installing any nuts.
11. 11

    Install and torque manifold nuts
    Install new self-locking nuts onto all studs. Apply anti-seize to nut threads if specified by stud manufacturer. Start all nuts by hand. Using a torque wrench, tighten nuts in a cross-pattern from center outward in three stages: first to 15 lb-ft, then to 25 lb-ft, then to final specification of 33 lb-ft. Recheck all nuts after final torque pass to ensure none have loosened.
    Torque spec

    Exhaust Flange Bolts45 Nm (33 lb-ft)
12. 12

    Reinstall turbocharger connection
    Position new turbo to manifold gasket. Carefully align turbocharger to exhaust manifold connection. Install turbocharger mounting bolts or V-band clamp. Apply anti-seize to flange bolt threads. Torque flange bolts evenly in cross-pattern to specification.
    Torque spec

    Exhaust Flange Bolts45 Nm (33 lb-ft)
13. 13

    Reinstall heat shield and exhaust components
    Reinstall exhaust manifold heat shield and torque bolts to specification. Reconnect exhaust downpipe to turbocharger outlet. Install and torque exhaust hanger bolts. Apply anti-seize to oxygen sensor threads (threads only, not sensor tip). Install oxygen sensor and torque to specification. Reconnect oxygen sensor electrical connector.
    Torque spec

    Heat Shield Bolts10 Nm (7 lb-ft)

    Hanger Bolts27 Nm (20 lb-ft)

    O2 Sensor45 Nm (33 lb-ft)

Reassembly

1. Reconnect battery cables, positive first then negative
2. Lower vehicle from jack stands if raised
3. Double-check all connections and torque specifications before starting engine

Verification

• Start engine and allow to reach operating temperature while monitoring for exhaust leaks at manifold
• Listen for any ticking or hissing sounds that would indicate a leak
• Visually inspect all connections for signs of exhaust gas escaping
• After first heat cycle, allow engine to cool and recheck manifold nut torque - retorque if any have loosened
• Check for diagnostic trouble codes related to oxygen sensor or exhaust system
• Test drive vehicle under various loads to ensure no exhaust leaks under operating conditions

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