Replace the flex pipe section of the exhaust system on a 2018-2024 Honda Accord 1.5L Turbo to repair leaks, cracks, or damage in the flexible coupling between the catalytic converter and exhaust system.

Warnings

Tools required

Parts

• Flex pipe assembly × 1 — Use OEM specification or compatible aftermarket
• Exhaust flange gasket × 2 — Use OEM specification
• Flange bolts and nuts × 4 — M10x1.25 bolts
• Exhaust hangers (if damaged) × 1 — Inspect and replace as needed

Preparation

1. Ensure engine and exhaust system are completely cool to the touch
2. Park vehicle on level surface and engage parking brake
3. Place wheel chocks behind rear wheels
4. Raise front of vehicle with floor jack and secure on jack stands at manufacturer-specified lift points
5. Spray all exhaust fasteners with penetrating oil and allow to soak for 30 minutes minimum
6. Visually inspect flex pipe location and identify all connection points

Procedure

1. 1

   Disconnect oxygen sensor
   Locate the upstream oxygen sensor on the exhaust pipe near the flex pipe. Disconnect the electrical connector by pressing the release tab. Using a 22mm O2 sensor socket, carefully unthread the sensor counterclockwise. Handle sensor carefully to avoid damage to the tip.
2. 2

   Remove heat shield if present
   If the flex pipe is covered by a heat shield, remove the mounting screws securing it using a 10mm socket. Set heat shield and hardware aside for reinstallation.
   Torque spec

   Cover Screws10 Nm (8 lb-ft)
3. 3

   Support exhaust system
   Position a jack stand or exhaust support under the mid-pipe section behind the flex pipe to prevent excessive movement when disconnecting components. Do not fully support weight, just stabilize the system.
4. 4

   Disconnect upstream flange
   Locate the flange connection between the catalytic converter and flex pipe inlet. Remove the two flange bolts and nuts using a 14mm socket and wrench. Separate the flange connection and remove the old gasket. Clean mating surfaces with a wire brush.
   ⚠If bolts are severely corroded and break, you may need to drill out broken studs and re-tap threads or use a repair flange kit.
   Torque spec

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

   Disconnect downstream flange or clamp
   Locate the connection between the flex pipe outlet and mid-pipe. If using a flange connection, remove the two flange bolts and nuts with a 14mm socket. If using a clamp connection, loosen the clamp bolts with a 12mm socket. Separate the connection and remove old gasket if applicable.
   Torque spec

   Flange Bolts45 Nm (33 lb-ft)

   Exhaust Clamps55 Nm (41 lb-ft)
6. 6

   Remove exhaust hanger supports
   Locate rubber exhaust hangers supporting the flex pipe section. Use a pry tool or pull downward to disconnect the metal hanger loops from the rubber mounts. Note the orientation for reassembly.
7. 7

   Remove old flex pipe
   With all connections and hangers disconnected, carefully maneuver the old flex pipe assembly out from under the vehicle. Inspect the removed component to confirm failure location and type of damage.
8. 8

   Clean all mating surfaces
   Thoroughly clean all flange mating surfaces on the catalytic converter and mid-pipe using a wire brush and gasket scraper. Remove all carbon buildup, old gasket material, and corrosion to ensure proper seal with new gaskets.
9. 9

   Install new flex pipe
   Position the new flex pipe assembly under the vehicle. Install new flange gaskets on both upstream and downstream connections. Align the flex pipe with both flange connections and insert flange bolts finger-tight. Ensure proper orientation of the flex section.
10. 10

    Reconnect exhaust hangers
    Attach the exhaust hanger loops to the rubber mounts in the same orientation as removal. Ensure hangers are fully seated and supporting the exhaust system weight evenly.
11. 11

    Torque flange connections
    Starting with the upstream flange, torque the flange bolts in a cross pattern to specification. Repeat for the downstream flange connection. If using clamp-type connection, torque exhaust clamp bolts to specification. Verify all connections are properly seated before final torque.
    Torque spec

    Flange Bolts45 Nm (33 lb-ft)

    Exhaust Clamps55 Nm (41 lb-ft)
12. 12

    Reinstall oxygen sensor
    Apply a small amount of anti-seize compound to the oxygen sensor threads (avoid getting compound on sensor tip). Thread the sensor into the bung by hand until snug, then torque to specification using the O2 sensor socket. Reconnect the electrical connector until it clicks.
    ⚠Do not over-torque oxygen sensor as this can damage the threads in the exhaust pipe and cause sensor failure.
    Torque spec

    O2 Sensor45 Nm (33 lb-ft)
13. 13

    Reinstall heat shield
    If a heat shield was removed, position it over the flex pipe and secure with the mounting screws. Torque screws to specification.
    Torque spec

    Cover Screws10 Nm (8 lb-ft)

Reassembly

1. Verify all exhaust connections are tight and properly torqued
2. Ensure all exhaust hangers are properly engaged in rubber mounts
3. Check that no wiring or components are in contact with hot exhaust parts
4. Remove jack stands and carefully lower vehicle to ground

Verification

• Start engine and allow to idle. Listen for any exhaust leaks at flex pipe connections
• Rev engine to 2000-3000 RPM and verify no abnormal sounds or leaks
• Check for any visible exhaust smoke or fumes escaping from flange connections
• Verify O2 sensor is functioning properly with no check engine light or sensor codes
• After test drive, re-inspect all connections for leaks while engine is at operating temperature
• Verify exhaust hangers are still properly seated and system is not sagging or contacting undercarriage

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