Exhaust Manifold

This procedure covers removal and replacement of the exhaust manifold on the 2018-2024 Toyota Camry 2.5L I4 engine, including gasket replacement and oxygen sensor handling.

Warnings

Tools required

Parts

• Exhaust manifold gasket × 1 — Use OEM specification
• Exhaust manifold nuts × 8 — Use OEM specification
• Exhaust flange gasket × 1 — Use OEM specification
• Heat shield gasket (if equipped) × 1 — Use OEM specification
• Engine coolant (if draining required) × 1 — Toyota Super Long Life Coolant (Pink)

Preparation

1. Ensure engine is completely cold to the touch
2. Disconnect negative battery terminal and wait 90 seconds for airbag system to discharge
3. Raise and secure vehicle on jack stands with front wheels elevated for underbody access
4. Remove engine splash shield/under cover to access exhaust components from below
5. Apply penetrating oil to all exhaust manifold nuts, flange bolts, and O2 sensor threads. Allow to soak while proceeding
6. Place drain pan under work area to catch any coolant or oil drips

Procedure

1. 1

   Remove engine cover and air intake components
   Remove the plastic engine cover by pulling upward on the retaining clips. Disconnect the air intake tube from the throttle body and remove the intake resonator to improve access to the top of the manifold. Set components aside in a clean area.
   Torque spec

   Cover Bolts16 Nm (12 lb-ft)
2. 2

   Disconnect oxygen sensor electrical connector
   Locate the oxygen sensor (upstream/front sensor) on the exhaust manifold. Press the release tab and disconnect the electrical connector. Unclip the wiring harness from any retaining clips along the manifold to provide clearance.
   ℹ️Mark connector orientation if not keyed to ensure proper reconnection.
   Torque spec

   Electrical Connector Bolts7 Nm (5 lb-ft)
3. 3

   Remove upstream oxygen sensor
   Using an O2 sensor socket or 22mm offset wrench, unthread the upstream oxygen sensor from the exhaust manifold. Turn counterclockwise. If sensor is seized, apply additional penetrating oil and allow to soak, or carefully apply heat with a torch while turning. Remove sensor completely and set aside.
   ⚠O2 sensor threads are easily damaged. Do not force if resistance is excessive. Applying moderate heat can help break corrosion bond.
   Torque spec

   O2 Sensor47 Nm (35 lb-ft)
4. 4

   Remove exhaust manifold heat shield
   Locate and remove all heat shield mounting bolts (typically 3-5 bolts depending on configuration). The heat shield is a metal cover over the manifold. Carefully lift shield away from manifold. Note the position of any spacers or washers for reassembly.
   ℹ️Heat shield bolts may be corroded and prone to breaking. Use penetrating oil and patience.
   Torque spec

   Heat Shield Bolts10 Nm (7 lb-ft)
5. 5

   Disconnect exhaust pipe from manifold
   From underneath the vehicle, locate the exhaust flange connection where the front pipe bolts to the exhaust manifold. Remove the two or three flange bolts/nuts securing the connection. Support the exhaust pipe with a jack or suspend with wire to prevent strain on downstream hangers. Separate the flange connection and remove the old gasket.
   ⚠Exhaust pipe may still contain residual heat or condensation. Wear gloves when handling.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
6. 6

   Remove exhaust manifold bracket (if equipped)
   Some configurations have a support bracket connecting the exhaust manifold to the engine block or transmission bell housing. Locate and remove the mounting bolts securing this bracket. Remove bracket to provide clearance for manifold removal.
   Torque spec

   Mounting Bolts47 Nm (35 lb-ft)
7. 7

   Remove exhaust manifold retaining nuts
   Working from the top of the engine, locate all exhaust manifold nuts (typically 8 nuts) securing the manifold to the cylinder head studs. Begin removing nuts in reverse order from cold-to-hot (start from outer edges, work toward center). Use a ratchet with appropriate extensions to access all nuts. Remove all nuts completely and retain for inspection.
   ⚠If a stud begins to turn with the nut, stop immediately. Apply additional penetrating oil and use two wrenches to hold stud while removing nut. Broken studs require extraction.
   Torque spec

   Exhaust Manifold Nuts30 Nm (22 lb-ft)
8. 8

   Remove exhaust manifold assembly
   Carefully lift the exhaust manifold away from the cylinder head. It may require gentle prying or wiggling to break the gasket seal. Work the manifold up and out of the engine bay, maneuvering around obstacles. Once removed, place on a clean work surface.
9. 9

   Remove old gasket and clean mating surfaces
   Remove the old exhaust manifold gasket from the cylinder head. Use a plastic gasket scraper to carefully remove all gasket material from both the cylinder head surface and the manifold mating surface. Use a wire brush to clean the surfaces thoroughly. Wipe clean with a shop towel. Cover the exhaust ports with clean towels to prevent debris entry.
   ⚠Do not gouge or scratch the aluminum cylinder head surface. Use only plastic scrapers on the head. Metal scrapers may be used carefully on the cast iron manifold.
   ⚠Ensure no gasket material falls into exhaust ports or onto valves.
   Torque spec

   Gasket Surface Bolts20 Nm (15 lb-ft)
10. 10

    Inspect manifold and studs
    Inspect the exhaust manifold for cracks, especially around the ports and mounting flanges. Check that all cylinder head studs are intact and not damaged. If any studs are broken or threads are damaged, they must be extracted and replaced before proceeding. Inspect the manifold flange for warping using a straight edge.
    ℹ️Manifold warpage exceeding 0.05mm requires manifold resurfacing or replacement.
11. 11

    Install new gasket and position manifold
    Remove shop towels from exhaust ports. Position the new exhaust manifold gasket onto the cylinder head studs, ensuring correct orientation (markings should face manifold). Carefully position the exhaust manifold onto the studs and align with gasket. Ensure manifold seats fully against the gasket.
12. 12

    Install and torque manifold nuts
    Apply anti-seize compound to the threads of new exhaust manifold nuts (or cleaned original nuts if in good condition). Thread all nuts onto studs by hand. Working from hot-to-cold (center to outer edges), torque nuts to 30 Nm (22 lb-ft) in a cross-pattern sequence. Verify with factory service manual for exact sequence pattern for this engine.
    ⚠Follow proper torque sequence to ensure even gasket compression and prevent warping. Consult service manual for specific pattern.
    Torque spec

    Exhaust Manifold Nuts30 Nm (22 lb-ft)
13. 13

    Reinstall exhaust manifold bracket and heat shield
    If equipped with a support bracket, reinstall and torque mounting bolts to specification. Position the heat shield over the manifold, aligning all bolt holes. Install heat shield bolts and torque to 10 Nm (7 ft-lb) following any specified sequence in the service manual.
    Torque spec

    Mounting Bolts47 Nm (35 lb-ft)

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

    Reconnect exhaust pipe to manifold
    Install new exhaust flange gasket between manifold and front pipe. Align exhaust pipe flange with manifold flange. Apply anti-seize to exhaust flange bolt threads. Install flange bolts and torque to 45 Nm (33 lb-ft) following any sequence specified in service manual. Ensure exhaust pipe hangers are properly positioned and not under strain.
    ℹ️Verify exhaust pipe alignment before final torque. Misalignment causes stress cracks and exhaust leaks.
    Torque spec

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

    Install oxygen sensor and reconnect electrical
    Apply a thin coat of anti-seize compound to the oxygen sensor threads (avoid getting compound on sensor tip). Thread O2 sensor into manifold by hand until seated, then torque to 47 Nm (35 lb-ft) using sensor socket. Reconnect the electrical connector until it clicks. Secure wiring harness to retaining clips.
    ⚠Do not overtighten O2 sensor. Excessive torque can damage sensor or threads.
    Torque spec

    O2 Sensor47 Nm (35 lb-ft)

Reassembly

1. Reinstall air intake components and engine cover in reverse order of removal
2. Reinstall engine splash shield/under cover from beneath vehicle
3. Reconnect negative battery terminal
4. Lower vehicle from jack stands

Verification

• Start engine and listen for exhaust leaks at manifold-to-head junction and manifold-to-pipe flange. A hissing sound indicates a leak requiring re-torque or gasket inspection
• Allow engine to reach operating temperature and visually inspect for any exhaust smoke or leaks around all connections
• Check that no warning lights are illuminated on the instrument cluster, particularly the check engine light related to O2 sensor
• Use scan tool to verify oxygen sensor is reading properly and providing data to ECU
• Perform a test drive and verify normal engine performance with no unusual noises or vibrations from exhaust system

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