Exhaust Manifold Studs

This procedure covers the removal and replacement of broken or damaged exhaust manifold studs on the 2015-2020 Ford F-150 5.0L Coyote V8 engine, including manifold removal and stud extraction.

Warnings

Tools required

Parts

• Exhaust manifold studs × 8 — Use OEM specification
• Exhaust manifold gaskets × 2 — Use OEM specification
• Exhaust manifold nuts × 16 — Use OEM specification
• Exhaust flange gaskets × 2 — Use OEM specification
• Heat shield bolts (if damaged) × 4 — Use OEM specification
• Oxygen sensor anti-seize × 1 — Nickel-based anti-seize

Preparation

1. Ensure engine is completely cold (minimum 3 hours since last operation)
2. Disconnect negative battery terminal and wait 10 minutes for airbag system to discharge
3. Raise and support vehicle safely on jack stands at appropriate lift points
4. Remove engine splash shield if equipped
5. Spray all exhaust manifold nuts and oxygen sensor threads with penetrating oil and allow to soak for 30 minutes minimum

Procedure

1. 1

   Remove oxygen sensors
   Using oxygen sensor socket, carefully remove both upstream oxygen sensors from the exhaust manifolds. Work slowly to avoid breaking sensors in the manifold. If sensors are seized, apply heat with propane torch to manifold (not sensor) for 2-3 minutes, then retry.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)
2. 2

   Disconnect exhaust pipes from manifolds
   Remove the exhaust flange bolts connecting the exhaust Y-pipe to both manifolds. Support the exhaust system with a jack or wire to prevent strain on hangers. Separate the exhaust pipe from the manifolds and remove old gaskets.
   Torque spec

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

   Remove heat shields
   Remove heat shield bolts from both exhaust manifolds. On driver side, may need to remove brake master cylinder cover for access. Remove heat shields and set aside. Inspect bolts and replace if damaged.
   Torque spec

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

   Remove manifold retaining nuts
   Working from center outward, carefully remove all exhaust manifold nuts. Use penetrating oil liberally if nuts are seized. Count nuts removed to ensure all are accounted for (8 per manifold). If studs spin or break during removal, note their locations.
   ⚠If studs begin to spin or break during nut removal, stop immediately and apply more penetrating oil. Breaking additional studs will increase repair time significantly.
   Torque spec

   Manifold Nuts42 Nm (31 lb-ft)
5. 5

   Remove exhaust manifolds
   Carefully pry manifolds away from cylinder heads using pry bar at designated pry points. Work evenly to avoid binding. Remove manifolds and old gaskets. Inspect manifolds for cracks or warping. Place manifolds on clean work surface.
   ℹ️Driver side manifold may require additional maneuvering around steering components. Passenger side typically has better access.
6. 6

   Assess broken studs
   Identify all broken or damaged studs. Determine if studs are broken flush, recessed, or protruding from cylinder head. Clean area around each broken stud with wire brush. Spray additional penetrating oil on broken stud threads and allow 15 minutes soak time.
   ⚠If more than 4 studs are broken on one side, or if studs are severely seized, consider cylinder head removal for proper extraction to avoid head damage.
7. 7

   Extract broken studs
   For protruding studs, use locking pliers or stud extractor. For flush/recessed studs: carefully center punch the exact center of each stud. Using progressively larger drill bits, drill pilot hole starting with 3mm bit. Drill straight and true to avoid damaging threads. Progress to size appropriate for your stud extractor (typically 6-7mm for M8 studs). Use left-hand drill bits if available as these may catch and remove stud while drilling. Insert appropriate size stud extractor and carefully turn counterclockwise. Apply penetrating oil frequently.
   ⚠️Keep drill perpendicular to cylinder head surface. Angled drilling will damage threads beyond repair and require helicoil installation or head removal.
   ⚠Have shop vacuum running continuously to capture all metal shavings. Cover open exhaust ports with tape or rags to prevent debris entry.
8. 8

   Clean and chase threads
   Once all broken studs are removed, thoroughly clean all stud holes with brake cleaner and compressed air. Run M8 x 1.25 thread chaser or tap through each hole to clean threads and verify condition. Inspect threads for damage. If threads are damaged, helicoil installation will be required (not covered in this procedure).
   ℹ️Use compressed air carefully to blow debris away from engine, not into exhaust ports or intake valley.
9. 9

   Install new exhaust studs
   Apply small amount of anti-seize to bottom 2-3 threads only of new studs. Thread studs into cylinder head by hand until seated. Use two nuts locked together on top of stud to tighten final 1/4 turn, or use stud installation tool. Ensure all studs are properly seated and protruding evenly. Verify stud height matches original configuration.
   ⚠Do not apply anti-seize to full length of stud threads as this can cause over-torquing and subsequent breakage. Only apply to threads entering cylinder head.
10. 10

    Prepare manifold mating surfaces
    Clean all gasket material from cylinder head mating surfaces using plastic scraper. Do not use metal scrapers that could gouge surfaces. Clean with brake cleaner and lint-free cloth. Inspect mating surfaces for damage or warping. Position new exhaust manifold gaskets on cylinder head, aligning with all stud locations.
    ℹ️Gaskets are typically designed to install without additional sealant. Do not use RTV or gasket maker unless specifically required by gasket manufacturer.
11. 11

    Install exhaust manifolds
    Carefully position exhaust manifolds onto studs and gaskets. Ensure manifolds seat fully against gaskets. Install new exhaust manifold nuts finger-tight on all studs. Verify manifold is properly aligned before tightening. Apply small amount of anti-seize to nut threads before installation.
    Torque spec

    Manifold Nuts42 Nm (31 lb-ft)
12. 12

    Torque manifold nuts
    Torque exhaust manifold nuts in three stages using spiral pattern from center outward: Stage 1 at 15 Nm (11 lb-ft), Stage 2 at 30 Nm (22 lb-ft), Stage 3 at final specification of 42 Nm (31 lb-ft). Allow 5 minutes between stages for gasket compression. Verify all nuts are torqued properly.
    ℹ️Proper torque sequence prevents gasket distortion and ensures even clamping force. Do not skip the multi-stage torque process.
    Torque spec

    Manifold Nuts42 Nm (31 lb-ft)
13. 13

    Install heat shields
    Position heat shields over manifolds and install heat shield bolts. Torque to specification. Ensure shields do not contact any moving components or wiring.
    Torque spec

    Heat Shield Bolts10 Nm (7 lb-ft)
14. 14

    Connect exhaust pipes
    Install new exhaust flange gaskets. Raise exhaust Y-pipe into position and align with manifold flanges. Install exhaust flange bolts with anti-seize on threads. Torque bolts evenly to specification. Verify exhaust system hangers are properly positioned and not under strain.
    Torque spec

    Exhaust Flange Bolts45 Nm (33 lb-ft)
15. 15

    Install oxygen sensors
    Apply nickel-based anti-seize to oxygen sensor threads only, keeping anti-seize away from sensor tip. Thread sensors into manifolds by hand until seated. Torque to specification using oxygen sensor socket. Connect electrical connectors to both sensors and verify clips are fully engaged.
    ⚠Do not get anti-seize on oxygen sensor element or electrical connector. Contamination will cause sensor failure and check engine light.
    Torque spec

    O2 Sensor45 Nm (33 lb-ft)

Reassembly

1. Reinstall engine splash shield if removed
2. Remove jack stands and lower vehicle to ground
3. Reconnect negative battery terminal
4. Clear any diagnostic trouble codes related to oxygen sensor disconnection using scan tool if available

Verification

• Start engine and allow to idle for 5 minutes, monitoring for exhaust leaks at manifold gaskets and flange connections
• Check for unusual noises or vibrations from exhaust system
• Verify no exhaust smell in cabin during operation
• Perform visual inspection of all connections while engine is running (from safe distance)
• After engine reaches operating temperature, shut off and allow to cool 30 minutes, then re-check all manifold nut torque values
• Test drive vehicle and verify no check engine light illuminates and normal engine performance
• After 100 miles of driving, re-torque manifold nuts to specification as final verification

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