Ask the Mechanic: Understanding the role of a catalytic converter

By: Tina Bakken
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The average consumer usually doesn’t need to think about their catalytic converter. But for those required to pass a state-mandated emissions test, or smog check, the catalytic converter plays a vital role. The definition of catalytic converter by Webster’s Dictionary is “A chemical filter connected to the exhaust system of an automotive vehicle to reduce air pollution.” If you define the word “catalyst” it means to hasten, but adding the word “converter,” in a sense, slows it down. Whatever emissions the engine on your car is puking out is filtered inside the catalytic converter so that whatever comes out is cleaner. The muffler muffles the sound; the catalytic converter muffles the emissions. You might not know there is anything wrong with your catalytic converter until you fail your smog check. Not that failure of the catalytic converter is the only reason to fail, but it is one of the most common reasons. Failing the emissions portion of your smog test means that the emissions readings detected by the test equipment at your mechanic’s shop exceeds the maximum allowed by the state of California. Quite often the catalytic converter is the culprit, as it has done its job for so long that it’s clogged or broken down inside. At this point, you would need to have it replaced and then retest your vehicle afterwards. The only way you could know there is a problem brewing prior to actually failing your smog test would be if you heard strange rattling noises from beneath your car. It’s not going to leak anything like a radiator would, so the noise is really the only way. Sometimes a rattle will develop when the guts of the catalytic converter are coming apart. But sometimes a rattle can mean something else, so have your mechanic check it out for you. In these tough economic times when people are pilfering anything that might bring fast cash, some thoughtless thieves are going around and unbolting catalytic converters from cars for the precious metals that make it up. Besides the obvious safeguards of parking your car in a locked garage or under a motion-sensor light, a vehicle owner can have the catalytic converter secured by their mechanic. These devices are made specific to the vehicle’s design and installation procedures vary. Some catalytic converters bolt on, while others are welded on. In order to deter thieves the bolt-on types can have their bolts spot welded by a professional, likely deterring the thieves from their 90-second grab. If you’re concerned about the condition of your catalytic converter, whether your vehicle is due for a smog check or not, seeking the advice of a professional is really the only way to know. And welding the bolts on yourself is not a good idea. There are too many flammable fluids and components that are at risk for the untrained weekend welder. So when it comes to the catalytic converter, leave it to the professionals. Tina Bakken is the owner of Tina’s Garage at 357 Nevada St., Suite 40, Auburn. She can be reached at (530) 885-8181.