If your vehicle has ever failed an emissions test then you know the importance of a working Catalytic Converter. This honeycomb shaped part of the emissions system is responsible for turning the toxic by-products produced by internal combustion into harmless gases like carbon-dioxide, nitrogen and water vapor. If you have the automotive skills and a "do-it yourself" attitude, you stand to save money by replacing your own.
Before attempting to change the part, make sure you are certain of its defect. Often times, a malfunctioning Catalytic Converter is indicative of another problem like misfiring spark plugs. Also take note if your vehicle has any work done for exhaust reasons, most notably the replacement of any pipes. Previous work done in these areas (like welds and cuts) can make it hard to make a clean switch.
If you are certain the catalytic converter needs to be changed out, locate it in your exhaust system between the exhaust manifold and the muffler. Be sure to put the car on a lift to safely maneuver underneath.
Lubricate the bolts by spraying a penetrating lubricant on them. Remove with a socket wrench. If bolts are rusted, let the lubricant stay on longer and replace with newer stainless steal ones when you are through.
Remove old converter. If previous welding makes this impossible, cutting will have to be done. A hammer can be used to help free the converter but be careful not to disturb other areas of the exhaust system.
Insert the new converter (using hammer if necessary) and bolt back together. If cutting took place, then welding will have to be done over the cut area to prevent leaks. In order to weld, clamp the areas together with an adjoining patch piece and weld the circumference of where the piece joins each side of the pipe.
Check your car for leaks by turning on the engine and lightly accelerating in park. If your converter is leaking, you will need to re-evaluate your welding skills.
