Exhaust Gasket - Rear

Replace the rear exhaust gasket between the center pipe and rear muffler section on the 2016-2021 Honda Civic 1.5L Turbo to eliminate exhaust leaks.

Warnings

Tools required

Parts

• Exhaust gasket - rear (donut gasket) × 1 — Use OEM specification
• Flange bolts (if corroded) × 2 — M10 x 1.25 x 40mm

Preparation

1. Ensure engine and exhaust system are completely cold to the touch
2. Park vehicle on level ground and engage parking brake
3. Spray penetrating oil on all rear exhaust flange bolts and allow to soak for 10-15 minutes
4. Safely raise and secure vehicle on jack stands at appropriate rear lift points
5. Visually inspect the rear exhaust flange connection location (between center pipe and rear muffler) to confirm access path

Procedure

1. 1

   Remove heat shield if equipped
   If a heat shield covers the rear flange connection, remove the 10mm mounting bolts securing it to the underbody. Set shield aside for reinstallation.
   Torque spec

   Heat Shield Bolts10 Nm (7 lb-ft)
2. 2

   Support rear muffler section
   Position a jack stand or block of wood under the rear muffler section to support its weight. This prevents the exhaust from hanging solely on the rubber hangers and makes flange separation easier.
3. 3

   Remove rear flange bolts
   Using a 14mm socket and ratchet, remove the two bolts securing the rear exhaust flange connection. If bolts are seized, apply additional penetrating oil and use a breaker bar. Keep bolts for inspection to determine if replacement is needed due to corrosion.
   ⚠Exhaust bolts may be severely corroded. Apply steady, controlled force to avoid shearing the bolt heads. If bolts break, extraction will be required.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
4. 4

   Separate exhaust sections
   Carefully pull the rear muffler section away from the center pipe. The joint may be stuck due to carbon buildup. Use gentle twisting motion if needed. Lower the rear section slightly on the support to create working clearance.
5. 5

   Remove old gasket and clean surfaces
   Remove and discard the old donut gasket from between the flanges. Use a wire brush and scraper to thoroughly clean both flange mating surfaces on the center pipe and rear muffler, removing all carbon deposits, rust, and old gasket material. Ensure surfaces are flat and smooth for proper seal.
   ℹ️A clean, flat mating surface is critical for preventing exhaust leaks. Spend adequate time on this step.
6. 6

   Inspect flange bolts and studs
   Examine the removed bolts for thread damage, excessive corrosion, or stretching. Check that threads in the flange are clean and undamaged. Replace bolts if threads are damaged or heads are rounded. Clean bolt threads with a wire brush.
7. 7

   Install new gasket
   Position the new donut gasket over the center pipe flange, ensuring it seats properly in the recess. The gasket should fit snugly without forcing. Verify the gasket is oriented correctly with any beveled edge facing the proper direction per gasket design.
8. 8

   Reconnect rear muffler section
   Carefully align the rear muffler flange with the center pipe flange, ensuring the gasket remains properly seated. Raise the rear section using your support until flanges mate completely. Verify alignment before inserting bolts.
9. 9

   Install and torque flange bolts
   Apply a thin coat of anti-seize compound to the threads of both flange bolts. Thread bolts by hand to ensure proper threading, then tighten in an alternating pattern (top bolt, then bottom bolt) to draw flanges together evenly. Torque bolts to specification using a torque wrench in the same alternating pattern.
   ℹ️Alternating tightening pattern ensures even gasket compression and prevents gasket distortion or leaks.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
10. 10

    Reinstall heat shield
    If a heat shield was removed, position it back in place and install the 10mm mounting bolts. Torque to specification. Ensure heat shield does not contact any moving components or create rattles.
    Torque spec

    Heat Shield Bolts10 Nm (7 lb-ft)
11. 11

    Check exhaust hanger alignment
    Verify all rubber exhaust hangers in the rear section are properly seated and the exhaust system hangs evenly with adequate clearance from underbody components, fuel lines, and suspension parts. Adjust if necessary.

Reassembly

1. Remove support from under rear muffler section
2. Verify all tools and materials are removed from under vehicle
3. Lower vehicle from jack stands safely

Verification

• Start engine and allow to idle, listening carefully for any exhaust leaks at the rear flange connection
• With engine running, carefully feel around the flange area (without touching hot components) for escaping exhaust gases
• Rev engine to 2000-2500 RPM and listen again for leaks under load
• Perform a short test drive and re-check for leaks, unusual exhaust noise, or rattles
• After test drive and cool-down, re-torque flange bolts to specification to account for gasket settling

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