This procedure covers removal and replacement of the catalytic converter downpipe assembly on a 2015 Kia Forte with 1.8L engine, including oxygen sensor handling and exhaust system connections.

Warnings

Tools required

Parts

• Downpipe/catalytic converter assembly × 1 — Use OEM specification or aftermarket equivalent
• Exhaust flange gasket (turbo to downpipe) × 1 — 28611-2B100
• Exhaust flange gasket (downpipe to midpipe) × 1 — 28741-2E000
• Exhaust flange nuts × 4 — As needed if corroded
• Heat shield hardware × 1 — As needed if damaged

Preparation

1. Ensure engine and exhaust system are completely cold
2. Raise vehicle securely on jack stands at all four corners to provide adequate working clearance
3. Apply penetrating oil to all exhaust flange bolts and oxygen sensor threads, allow to soak for at least 15 minutes
4. Inspect downpipe heat shields and mounting points for damage or excessive corrosion
5. Have fire extinguisher nearby when working under vehicle with exhaust components

Procedure

1. 1

   Disconnect battery negative terminal
   Disconnect the negative battery terminal to prevent oxygen sensor codes during removal. Use a 10mm wrench to loosen the terminal clamp and move the cable aside.
2. 2

   Remove heat shields
   Locate and remove the heat shields covering the downpipe and catalytic converter. Remove all heat shield mounting bolts and carefully remove shields. Some shields may be in multiple sections. Note the position and orientation of each shield for reinstallation.
   ⚠Heat shield bolts are often corroded and may strip easily. Use proper size tools and apply steady pressure.
   Torque spec

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

   Remove upstream oxygen sensor
   Disconnect the electrical connector from the upstream (pre-cat) oxygen sensor located on the downpipe near the turbo flange. Use a 22mm oxygen sensor socket and ratchet to remove the sensor by turning counterclockwise. Keep the sensor in a clean location if reusing.
   ⚠Oxygen sensors are fragile. Do not drop or allow oil/grease to contact the sensor tip. If sensor is seized, apply heat carefully to the boss, not the sensor body.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)
4. 4

   Remove downstream oxygen sensor
   Disconnect the electrical connector from the downstream oxygen sensor located after the catalytic converter. Use a 22mm oxygen sensor socket to remove the sensor. This sensor may be more accessible from under the vehicle.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)
5. 5

   Disconnect exhaust hanger
   Locate the rubber exhaust hanger that supports the downpipe assembly. Use a pry bar or large screwdriver to carefully separate the hanger from its mounting bracket. Support the exhaust to prevent excessive movement.
   Torque spec

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

   Remove upper flange bolts
   Remove the three bolts connecting the downpipe to the turbocharger outlet flange. Use a 14mm socket and wrench, holding the nut on the backside while turning the bolt. Work bolts evenly in a cross pattern. Allow the downpipe to hang supported by the lower flange connection.
   ⚠These bolts are under high thermal stress and may be severely corroded. If bolts begin to twist off, stop and apply additional penetrating oil and heat if necessary.
   Torque spec

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

   Remove lower flange bolts
   Remove the two or three bolts connecting the downpipe to the mid-pipe at the rear flange. Use a 14mm socket and wrench combination. Once all bolts are removed, carefully lower the downpipe assembly from the vehicle. The assembly is heavy and awkward, use care to avoid damaging other components.
   ⚠Downpipe assembly weighs approximately 15-20 lbs and may contain residual exhaust soot and condensation. Have a clean work area prepared.
   Torque spec

   Exhaust Flange Bolts45 Nm (33 lb-ft)
8. 8

   Clean flange surfaces
   Use a wire brush and scraper to thoroughly clean all flange mating surfaces on both the turbocharger outlet and the mid-pipe inlet. Remove all old gasket material, carbon buildup, and corrosion. Surfaces must be flat and clean for proper sealing.
9. 9

   Prepare new downpipe
   Inspect the new downpipe for shipping damage and verify all mounting points align correctly. Apply anti-seize compound to the oxygen sensor threads (threads only, not the sensor tip). Install both oxygen sensors hand-tight into the new downpipe before installation.
   ⚠Never apply anti-seize or any lubricant to the oxygen sensor tip. Contamination will destroy the sensor.
   Torque spec

   O2 Sensor45 Nm (33 lb-ft)
10. 10

    Install new downpipe assembly
    Position new exhaust flange gaskets on both the upper and lower flanges. Carefully lift the new downpipe into position, aligning first with the turbocharger outlet flange. Start all upper flange bolts hand-tight, then align the lower flange and start those bolts hand-tight. Ensure the downpipe is properly seated in the exhaust hanger before tightening any fasteners.
11. 11

    Torque upper flange bolts
    Apply anti-seize compound to the upper flange bolt threads. Torque the three upper flange bolts in a cross pattern to specification. Make multiple passes, increasing torque gradually to ensure even gasket compression.
    Torque spec

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

    Torque lower flange bolts
    Torque the lower flange bolts connecting the downpipe to the mid-pipe to specification. Again, use a cross pattern and multiple passes for even torque distribution.
    Torque spec

    Exhaust Flange Bolts45 Nm (33 lb-ft)
13. 13

    Torque oxygen sensors
    Using the 22mm oxygen sensor socket and torque wrench, tighten both oxygen sensors to specification. Connect both electrical connectors and ensure wiring is routed away from heat sources and moving components.
    Torque spec

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

    Reinstall heat shields
    Reinstall all heat shield sections in the correct orientation. Install and torque all heat shield mounting bolts. Ensure shields do not contact the downpipe directly and have proper clearance.
    Torque spec

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

    Reconnect battery and clear codes
    Reconnect the negative battery terminal. Start the engine and allow it to idle. Check all connection points for exhaust leaks (listen for hissing sounds). The check engine light may be illuminated due to oxygen sensor disconnection; use an OBD-II scanner to clear codes after verifying no new fault codes are present.

Reassembly

1. Verify all exhaust hangers are properly seated and not over-stretched
2. Ensure all heat shields are properly installed and not contacting exhaust pipes directly
3. Double-check that oxygen sensor wiring is secured and routed away from hot exhaust components
4. Verify no tools or parts were left in the engine bay or under the vehicle

Verification

• Start engine and listen carefully at all flange connections for exhaust leaks while engine is cold
• Allow engine to reach operating temperature and recheck for leaks as gaskets seat
• Use OBD-II scanner to verify both oxygen sensors are reporting properly and no exhaust-related codes are present
• Test drive vehicle and verify no exhaust rattle, vibration, or unusual sounds are present
• After 50-100 miles, recheck all flange bolt torque as gaskets may settle slightly

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