This procedure covers removal and installation of the downpipe (front exhaust pipe) connecting the exhaust manifold to the catalytic converter on 2014-2019 Toyota Corolla 1.8L models.

Warnings

Tools required

Parts

• Downpipe/Front exhaust pipe × 1 — Use OEM specification
• Exhaust flange gasket (manifold to downpipe) × 1 — 17173-0T020 or equivalent
• Exhaust flange gasket (downpipe to catalytic converter) × 1 — Use OEM specification
• Exhaust flange nuts × 4 — 12mm copper nuts (as needed)
• Heat shield bolts × 1 — Use OEM specification

Preparation

1. Ensure engine and exhaust system are completely cold
2. Apply penetrating oil to all exhaust flange bolts, heat shield bolts, and O2 sensor threads
3. Raise vehicle safely and support on jack stands at manufacturer-specified lift points
4. Remove engine splash shield/undercover if equipped using 10mm socket
5. Disconnect negative battery terminal if working near O2 sensor wiring

Procedure

1. 1

   Disconnect oxygen sensor
   Locate the upstream oxygen sensor in the downpipe. Disconnect the electrical connector by pressing the release tab. If removing the sensor completely, use a 22mm O2 sensor socket to carefully unthread it counterclockwise. Avoid damaging the sensor threads or connector.
2. 2

   Remove heat shields
   Remove any heat shields covering the downpipe and exhaust manifold connection points using a 10mm socket. There are typically 2-3 shields in this area. Set shields and bolts aside for reinstallation.
   Torque spec

   Heat Shield Bolts10 Nm (7 lb-ft)
3. 3

   Support exhaust system
   Position a jack or support under the catalytic converter/exhaust system downstream of the downpipe to prevent the exhaust from dropping when the downpipe is disconnected. Use a block of wood between jack and exhaust to prevent damage.
4. 4

   Disconnect downpipe from catalytic converter
   Locate the flange connection between the downpipe and catalytic converter. Remove the 2 flange bolts/nuts (typically 14mm) at this connection. Use a breaker bar if necessary. If bolts are seized, apply heat carefully or additional penetrating oil. Separate the flange connection.
   ⚠Seized exhaust bolts may snap during removal. Have replacement hardware available.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
5. 5

   Remove exhaust hanger support
   If the downpipe has a rubber hanger mount, remove the hanger bolt or unhook the hanger from its bracket. This varies by exact configuration but typically uses a 12mm or 14mm bolt.
   Torque spec

   Hanger Bolts19 Nm (14 lb-ft)
6. 6

   Disconnect downpipe from exhaust manifold
   Locate the flange connection at the exhaust manifold (typically 2 nuts/bolts accessed from below). Remove the exhaust flange bolts/nuts using appropriate socket (typically 14mm). Work bolts evenly to prevent binding. Once fasteners are removed, pull downpipe away from manifold studs.
   ⚠Exhaust manifold studs can break if downpipe is forced. Wiggle gently to separate if stuck on studs.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
7. 7

   Remove downpipe
   Maneuver the downpipe out from underneath the vehicle. It may need to be rotated or angled to clear suspension components and the subframe. Remove and discard old exhaust gaskets from both flange surfaces.
8. 8

   Clean mating surfaces
   Use a wire brush to thoroughly clean the exhaust manifold flange surface and the catalytic converter flange surface. Remove all old gasket material, carbon deposits, and corrosion. Inspect flange surfaces for warping or damage. Clean exhaust manifold studs with a wire brush.
9. 9

   Install new gaskets and position downpipe
   Install new exhaust flange gaskets at both the manifold and catalytic converter connections. Apply a thin coat of anti-seize to exhaust manifold studs. Position the new or cleaned downpipe into place, aligning with manifold studs first, then align with catalytic converter flange.
   ℹ️Ensure gaskets are properly seated and oriented before installing fasteners.
10. 10

    Install exhaust manifold flange bolts
    Apply anti-seize to the threads of new or cleaned exhaust flange bolts/nuts. Thread bolts by hand first to ensure proper alignment. Tighten the exhaust manifold flange bolts evenly in a cross pattern to the specified torque.
    Torque spec

    Exhaust Flange Bolts45 Nm (33 lb-ft)
11. 11

    Install catalytic converter flange bolts
    Apply anti-seize to flange bolt threads. Install and hand-thread the flange bolts connecting the downpipe to the catalytic converter. Tighten evenly to the specified torque.
    Torque spec

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

    Reinstall exhaust hanger
    Reconnect the exhaust hanger to its mounting bracket or reinstall the hanger bolt. Ensure the rubber hanger is not twisted or over-stretched. Tighten hanger bolt to specification.
    Torque spec

    Hanger Bolts19 Nm (14 lb-ft)
13. 13

    Install oxygen sensor
    If the O2 sensor was removed, apply a small amount of anti-seize compound ONLY to the sensor threads (avoid getting anti-seize on the sensor tip or connector). Thread the sensor into the downpipe by hand, then tighten to specification using the 22mm O2 sensor socket. Reconnect the electrical connector ensuring it clicks into place.
    ⚠Never apply anti-seize to the O2 sensor tip or electrical connector. Only apply to threads.
    Torque spec

    O2 Sensor45 Nm (33 lb-ft)
14. 14

    Reinstall heat shields
    Position heat shields over the downpipe and exhaust manifold area. Install and tighten heat shield bolts to specification. Ensure heat shields do not contact moving components or create rattle points.
    Torque spec

    Heat Shield Bolts10 Nm (7 lb-ft)
15. 15

    Reinstall undercover and lower vehicle
    Reinstall the engine splash shield/undercover if equipped. Remove jack stands and carefully lower the vehicle. Reconnect the negative battery terminal if it was disconnected.

Reassembly

1. Verify all exhaust connections are secure and properly torqued
2. Ensure O2 sensor wiring is routed away from hot exhaust components and moving parts
3. Check that all heat shields are properly secured and not touching moving components
4. Verify exhaust hangers are properly seated and supporting the system weight

Verification

• Start the engine and listen for exhaust leaks at both flange connections. A leak will produce a ticking or hissing sound that increases with RPM
• Allow engine to reach operating temperature and inspect all connections for signs of exhaust gas leakage (soot marks or smell)
• Check for any rattles or unusual noises from the exhaust system at idle and while revving
• Verify O2 sensor is functioning properly - check engine light should not illuminate for O2 sensor codes after several drive cycles
• Inspect underneath vehicle after test drive to ensure no exhaust components are contacting the chassis or suspension

More procedures for this vehicle