This procedure covers the removal and replacement of the muffler assembly on a 2016-2021 Honda Civic with the 1.5L turbocharged engine.

Warnings

Tools required

Parts

• Muffler assembly × 1 — Use OEM specification or equivalent
• Exhaust gasket (flange) × 1 — 18115-5AA-A00
• Rubber exhaust hangers × 2 — Replace if damaged

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 front wheels
4. Apply penetrating oil to all exhaust flange bolts, clamp bolts, and hanger bracket bolts
5. Raise rear of vehicle using floor jack and support securely on jack stands at manufacturer-recommended lift points
6. Verify vehicle is stable before working underneath

Procedure

1. 1

   Locate and inspect muffler assembly
   Position yourself under the rear of the vehicle. Locate the muffler assembly at the rear of the exhaust system. Identify the connection point at the center pipe flange (forward connection), the two rubber exhaust hangers supporting the muffler, and the exhaust outlet at the rear bumper. Inspect the condition of surrounding components.
2. 2

   Support muffler assembly
   Use a floor jack with a block of wood or exhaust support stand to gently support the weight of the muffler assembly from below. Position support near the center of the muffler body to prevent it from falling when hangers are released. Do not apply upward pressure, only light support.
3. 3

   Remove flange connection bolts
   Locate the two-bolt flange connection between the center pipe and muffler inlet. Using a 14mm socket and wrench, remove both flange bolts while holding the nuts on the opposite side to prevent spinning. Separate the flange connection slightly but leave muffler supported on hangers. Remove and discard the old exhaust gasket.
4. 4

   Disconnect rear exhaust hanger
   Locate the rear rubber exhaust hanger near the muffler outlet. Using a rubber hanger removal tool or by hand with penetrating oil as lubricant, carefully work the metal hanger hook out of the rubber mounting grommet. Pull the hanger downward and twist to release. Inspect rubber grommet for cracking or deterioration.
5. 5

   Disconnect middle exhaust hanger
   Locate the middle rubber exhaust hanger on the muffler body. Using the same technique, carefully release the metal hanger hook from the rubber mounting grommet. With both hangers released, the muffler should rest entirely on your support jack.
6. 6

   Remove muffler assembly
   Slowly lower the support jack while guiding the muffler assembly down and toward the rear of the vehicle. Angle the muffler as needed to clear the rear suspension components and exhaust outlet opening in the rear bumper. Remove muffler from under vehicle.
7. 7

   Clean flange mating surface
   Using a wire brush, thoroughly clean the flange surface on the center pipe where it connects to the muffler. Remove all carbon deposits, rust, and old gasket material to ensure a clean, flat seating surface for the new gasket. Inspect flange for cracks or damage.
8. 8

   Prepare new muffler assembly
   Unpack new muffler assembly and verify it matches the original configuration including hanger positions and inlet/outlet dimensions. Install new rubber hangers onto the muffler hanger hooks if replacements are needed. Apply a thin coat of anti-seize compound to the threads of the new flange bolts.
9. 9

   Position new muffler assembly
   Place new muffler on support jack and raise into approximate position under vehicle. Align the muffler inlet with the center pipe flange. Angle and maneuver as necessary to feed the exhaust outlet tip through the rear bumper opening while positioning hanger hooks below their rubber grommets.
10. 10

    Install exhaust hangers
    Starting with the middle hanger, use penetrating oil or soapy water as lubricant and work the metal hanger hook into the rubber mounting grommet. Apply firm upward pressure and twist to fully seat. Repeat for the rear hanger. Ensure both hangers are fully engaged and supporting the muffler weight evenly.
11. 11

    Install flange gasket and connect flange
    Position the new exhaust gasket onto the center pipe flange, aligning the bolt holes. Raise the muffler inlet to mate with the center pipe flange, sandwiching the gasket between them. Verify proper alignment of all bolt holes and that gasket is not pinched or misaligned.
12. 12

    Install and torque flange bolts
    Insert both flange bolts with anti-seize applied through the flange and start the nuts by hand on the opposite side. Tighten bolts gradually in an alternating pattern to draw the flanges together evenly. Using a torque wrench, torque both flange bolts to specification in a criss-cross pattern to ensure even gasket compression and seal.
    ⚠Anti-seize compound must be applied to flange bolt threads as specified. Overtightening without anti-seize can cause bolt failure or stripping.
13. 13

    Verify muffler alignment and clearances
    Remove support jack from under muffler. Verify the exhaust tip is centered in the rear bumper cutout with adequate clearance on all sides. Check that the muffler body has at least 25mm (1 inch) clearance from suspension components, fuel tank, and underbody panels throughout its length. Adjust hanger positions if necessary by releasing and re-seating in grommets.

Reassembly

1. No additional reassembly steps required beyond the installation procedure above
2. Ensure all exhaust hangers are fully seated and supporting the muffler assembly
3. Verify exhaust tip position and alignment before lowering vehicle

Verification

• With vehicle still on jack stands, visually inspect all connections for proper alignment and adequate clearances
• Verify flange connection is tight with no visible gaps at the gasket
• Confirm both rubber exhaust hangers are fully engaged and not stressed or twisted
• Lower vehicle to ground and remove jack stands
• Start engine and allow to idle. Listen for exhaust leaks at the flange connection (hissing or ticking sounds indicate leak)
• With engine running, walk around vehicle and verify no unusual exhaust noise or rattles
• Rev engine to 2500-3000 RPM briefly and listen for leaks or vibrations
• Visually inspect under vehicle while engine is running for any exhaust smoke from connections indicating leak
• After test drive, allow exhaust to cool and re-check flange bolt torque
• Verify exhaust tip remains centered in bumper cutout and has no contact with bumper or body panels

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