How to Change a Catalytic Converter

A catalytic converter is the part of a car's exhaust system that helps reduce air pollution.

While not generally considered a do-it-yourself project, changing a catalytic converter is not a complicated operation. The problem with changing any part of the exhaust system is that it is located underneath the car and is not usually easy to remove. It sounds simple---you unbolt a few things and pull the exhaust loose. However, you will have to deal with heavy pieces of metal that may be rusted into place. Most backyard mechanics do not have a car lift, so exhaust work must be done while lying under the car on your back looking up.

Things You'll Need

• Catalytic converter assembly
• Ratchet
• Socket set
• Wrench
• Jack
• Jack stand
• Rubber lubricant

Instructions

1. Look under the car and see which side the catalytic converter is closer to. Block the tires so that the car will not move while it is raised on the jack. Use a jack and raise the corner of the car that will give you the best access to the catalytic converter. If you have a jack stand, place it so that you can lower the jack until the weight of the car rests mostly on the jack stand. Leave the jack in place to prevent the car from dropping while you are under it.

2. Slide under the car and locate the oxygen sensor that is in the exhaust line near the catalytic converter on most cars. Use a wrench and unscrew it from the exhaust system. Loosen the clamp between the catalytic converter and the engine with a ratchet and socket. Slide the clamp forward to let the pipe attached to the converter drop loose.

3. Find the coupling between the catalytic converter and the muffler. It will be held together with two bolts. Use the ratchet and socket to remove these two bolts. The catalytic converter and the associated exhaust pipe should be hanging from one or two muffler hangers under the car.

4. Wiggle the entire assembly back and forth until the pins slide out of the rubber bushings that hold the catalytic converter up against the underside of the car. You may need to use a little rubber lubricant, which can be purchased at an auto parts store, to make this process easier. The lubricant comes in a squeeze bottle from which you can squirt small amounts around the converter to loosen it. Bring the converter down to the ground and pull it out from under the car.

5. Compare the new converter to the old one to make sure that it is identical. Slide the new assembly under the car to the approximate position where it will be installed. Lift the catalytic converter and push the pins into the muffler hangers. Install the two bolts back into the coupling with the ratchet and socket.

6. Line up the pipe on the other side of the catalytic converter and replace the clamp. Tighten it with the ratchet and socket. Use the wrench to screw the oxygen sensor back into the exhaust pipe. Raise the jack enough to remove the stand and lower the car back to the ground to complete the job.

Tips & Warnings

• Always make sure that a car is well supported before crawling under it.

References

• They might be racing: How to replace the catalytic converter assembly