How to Replace a Catalytic Converter
Safely lift the vehicle, unbolt the rusted exhaust flanges, remove the faulty catalytic converter, and install a direct-fit replacement with fresh gaskets.
- Read the tools, materials, safety notes, and steps below for free.
- Tap Start Camera Coach when you want hands-free voice help.
- Allow camera and microphone. Point your phone at the work; the coach watches your progress and tells you the next step.
🧰 Required Tools & Equipment
- ✓ Hydraulic floor jack and rated jack stands
- ✓ 3/8-inch and 1/2-inch drive ratchet and socket set
- ✓ Penetrating oil (e.g., PB B'laster or Kroil)
- ✓ Oxygen sensor socket
- ✓ Torque wrench
- ✓ Wire brush
- ✓ Safety glasses and mechanic gloves
📦 Materials & Supplies
- ✓ Direct-fit replacement catalytic converter
- ✓ New exhaust flange gaskets
- ✓ Exhaust flange hardware (grade 8 bolts and locknuts)
- ✓ Anti-seize compound
⚠️ Safety Checkpoints & Warnings
- • Vehicle must be fully cold to the touch before starting work to prevent severe burns from exhaust components.
- • Vehicle must be resting securely on weight-rated jack stands placed on solid, level ground with wheels chocked.
- • Eye protection must be worn continuously to guard against falling rust flakes and penetrating spray.
📋 Step-by-Step Guide (7 Steps)
Raise and Secure the Vehicle
Park on a flat concrete surface, apply the parking brake, and chock the rear wheels. Lift the vehicle using a floor jack at the factory lift points and set it securely onto jack stands at all four corners.
- • Jack stands fully engaged with frame rails or pinch welds
- • Vehicle completely off ground with jack lowered slightly to transfer weight onto stands
- • Relying solely on a hydraulic jack without stands
- • Lifting on an uneven surface
Soak Hardware and Disconnect O2 Sensors
Locate the upstream and downstream oxygen sensors mounted in or near the catalytic converter. Unplug their electrical harnesses and use an O2 sensor socket to unscrew the sensors, then douse all exhaust flange bolts thoroughly with penetrating oil.
- • O2 sensor wire harnesses unclipped and tied away from work area
- • Sensors completely removed without damaged wiring
- • Twisting the wire harness while turning the sensor instead of unclipping it first
Unbolt Exhaust Flanges
Use a six-point socket and breaker bar to loosen and remove the fasteners at the front and rear exhaust flanges. Support the converter with your hand or a stand as the final bolt comes free.
- • All mounting bolts removed from inlet and outlet flanges
- • Catalytic converter hanging free or resting on a support stand
- • Using a 12-point socket that rounds off severely corroded bolt heads
Remove Old Unit and Clean Flange Mating Surfaces
Drop the old catalytic converter down and remove it from under the vehicle. Use a wire brush or gasket scraper to clean the mating surfaces on the manifold pipe and cat-back exhaust pipe until bare, flat metal is visible.
- • Old converter out from under car
- • Exhaust flange faces free of old crushed gasket material and scale
- • Leaving fragments of the old crushed gasket stuck to the mating flange
Install New Converter with Fresh Gaskets
Position the new exhaust gaskets against the mating flanges and lift the new converter into place. Insert fresh grade 8 bolts and start nuts by hand on both ends to hang the pipe securely without tightening fully.
- • New catalytic converter suspended in correct flow orientation with all bolts started by hand
- • Gaskets correctly aligned between flange holes
- • Installing the converter backwards (against flow arrow)
- • Cross-threading new nuts onto bolts
Torque Hardware and Reinstall O2 Sensors
Tighten flange bolts evenly in an alternating pattern, then torque to manufacturer specification (typically 25–35 ft-lbs). Coat O2 sensor threads lightly with anti-seize (avoiding the sensor tip), screw them into their bungs, torque firmly, and plug in the electrical connectors.
- • Flanges pulled completely flush and parallel
- • O2 sensor harness connectors snapped securely into retaining clips
- • Getting anti-seize compound on the active sensor tip
- • Uneven bolt tension causing flange gaps
Start Engine and Inspect for Leaks
Lower the vehicle to the ground, start the engine, and let it idle. Listen for sputtering noises and hold a gloved hand 2 inches away from the flanges to feel for escaping exhaust pulses.
- • Engine idling smoothly without ticking or hissing exhaust noises
- • No smoke or turbulent gas escaping around flange joints
- • Touching bare skin directly to hot exhaust joints during running inspection
Credit: inspired by an original tutorial by WVW — watch the original on YouTube.
Don’t have everything?
- No Oxygen sensor socket? 22mm (7/8-inch) open-ended wrench
- No Penetrating oil? 50/50 mix of automatic transmission fluid (ATF) and acetone