What is a catalytic converter and where is it located?
The catalytic converter, also referred to as a cat converter, is part of an automobile’s exhaust system. It converts exhaust gasses such as carbon monoxide and nitrogen oxides produced by partial combustion of fuel in the engine, which are harmful to both the environment and to humans, into harmless carbon dioxide, water vapor, and nitrogen gas. During the 1970s, the Environmental Protection Agency (EPA) introduced a series of regulations aimed at reducing hazardous exhaust emissions from cars and trucks. All automobiles driven in the US and built after 1975 must be equipped with a catalytic converter. Without a working catalytic converter, your vehicle will pollute the environment, fail inspection, and be unable to drive legally.
The catalytic converter assembly can be found on the underside of your vehicle, either towards the front or the rear depending on the car or truck. On some vehicles, most commonly BMWs and many other newer cars and trucks, you will find a dual catalytic converter configuration. So, rather than having one cat converter to handle the task of converting the toxic emissions produced by the vehicle into less toxic ones, the vehicle will have two: one in front of the other (identified as front and rear). As emissions standards become harder to meet, you can probably expect to see this more often.
So, how does it all work? Well, the catalytic converter receives toxic exhaust gas from the front exhaust pipe, alters the chemicals in that gas to make it less toxic, and passes it on to the rear exhaust pipe through the muffler and out the tailpipe. The internal surface of the catalytic converter is made up of a ceramic material coated with chemicals that interact with the exhaust gasses to recombine them into more benign byproducts. These “catalysts” include metals like platinum, palladium, and rhodium. Cat converters have either a honeycomb or a beaded structure inside them to increase their internal surface area. This allows more of the catalyst to come in contact with the exhaust. Common problems with the catalytic converter stem from damage to the internal structure leading to clogging or chemical interactions, causing the catalysts to not work as well. This latter process is sometimes referred to as “catalytic poisoning.”
How do I know if my catalytic converter needs to be replaced?
There are a number of potential causes of automotive catalytic converter failure as well as a number of symptoms that might hint that your catalytic converter is not functioning as it should. Let’s take a look at some of those in detail.
Causes of Failure:
As mentioned above, the two major causes of catalytic converter failure are clogging and catalytic poisoning. The ceramic catalyst can also suffer road damage and be fractured.
Melting cermaics causes clogging. The exhaust gasses that pass through are very hot and cause the converter to heat up. If the air-fuel mix is too rich, unburned fuel can pass through to the exhaust system. Any fuel that leaves the combustion chamber unburned will enter the exhaust system and ignite when it reaches the catalytic converter. This can heat the converter far above normal operating conditions and cause a partial or complete meltdown of the ceramic catalyst. Besides a bad air fuel mixture, other possible causes of excess fuel in the exhaust are incorrect timing, corroded spark plugs or wires, a faulty oxygen sensor, a sticking float, faulty fuel injector, or a malfunctioning check valve.
In addition to melted ceramics, clogs can also be caused by carbon deposits. Sometimes oil or antifreeze can enter the exhaust through various leaks. If this occurs, the invasive chemicals may be ignited and leave behind a sooty residue that can block the flow of gases. This blockage creates an increase in backpressure and causes heat and exhaust to back up into the engine compartment. Your engine may actually draw burnt exhaust gasses back into the combustion chamber and dilute the efficiency of the next burn cycle. The result is a loss of power and over-heated engine components.
When these chemicals get into the catalytic converter, they can also lead to catalyst poisoning. These chemicals can interact with the catalyst chemicals and change them. Once they’ve been altered they will no longer interact effectively with the exhaust gasses to convert them, which of course prevents the catalytic converter from doing its job of reducing harmful exhaust emissions.
While the outside of the converter is made of sturdy metal, the ceramics inside are fragile and thin-walled. It is protected by a dense, insulating mat. This mat holds the catalyst in place and provides moderate protection against damage. However, rock or road debris striking the converter or a broken exhaust system support can cause a catalyst fracture, as can potholes or off-road driving. Once the ceramic catalyst is fractured, the broken pieces become loose and rattle around and break up into smaller pieces. Much like in a clog, flow is interrupted and back pressure in the exhaust system increases. This leads to heat build-up and loss of power. So, how will you know if one of the problems has occurred?
Symptoms of Failure:
There are a number of signs that point to problems with the cat converter, ranging from the obvious to the subtle. If your car or truck fails an emissions inspection, the catalytic converter is a likely culprit. If it isn’t working properly it may also lead to a bad reading on your downstream oxygen sensor, which will cause your check engine light to come on.
A rattling sound from the converter likely indicates the catalyst is fractured. Catalyst fracture and clogging can both lead to back pressure in the exhaust system. When this happens, it becomes more difficult for the engine to take in more air, which can reduce engine power. There may come a point where you step on the gas and the car simply won’t go any faster. Eventually, it could get so bad that the engine runs only briefly before shutting down. Clogs or fractures may also present a drop in gas mileage or rough idling.
If catalytic poisoning has occurred, then more chemicals will remain unchanged in the exhaust, making your cars emissions more noxious than usual. You may notice the exhaust gas being much darker than usual or having a sulfurous, rotten egg smell.
Can I replace the catalytic converter myself?
Catalytic converters are meant to last the lifetime of your vehicle. If you are having catalytic converter problems, then odds are there is another problem which caused it. It would be wise to find the source of the problem and fix it at the same time, or you’ll quickly be looking to replace another converter.
That being said, whether or not you can replace the converter yourself depends on whether you have the necessary equipment and mechanical skill for the job, and on whether the piece is bolted to the vehicle or welded on.
First, you'll have to raise the vehicle. Then, depending on whether your exhaust system has been modified or replaced, you may have to do some cutting and welding. If your catalytic converter assembly is only connected by bolts, then it's a simple job. Lubricate and unhook the clamps, remove the converter (a hammer may help with this), and insert the new direct fit catalytic converter. A patch piece may be needed to prevent leaks, or you could weld the connection closed.
If the catalytic converter assembly is welded on, then you'll have to do some cutting to remove the old one. Be aware of wiring and fuel lines when working. This is more difficult and can be dangerous and you may need to seek a professional.
Need a direct fit catalytic converter replacement?
As mentioned earlier, every automobile built after 1975 must be equipped with a cat converter assembly – it’s the law. If your car or truck’s cat converter has been damaged or is no longer working properly, your car or truck will produce a great deal of air pollution which is not good for the environment or for people’s health. Your car or truck will also fail inspection and you will not be able to legally drive it. Because of these reasons, if you are in need of a replacement catalytic converter, it’s critical that you obtain one immediately.
At 1A Auto, we carry aftermarket, direct fit catalytic converters for many makes and models. Our aftermarket catalytic converters are designed to exact specifications ensuring proper, direct fit; they come with the correct pipes, flanges and connections for easy removal of your stock converter and installation of your replacement catalytic converter. They are also constructed from top materials, such as 409 stainless steel, for maximum durability. Each cat converter comes with a warranty guaranteeing it will pass Federal EPA emissions standards for 25,000 miles. They also carry a Limited Manufacturers Warranty against defects in material or workmanship for 5 Years or 50,000 miles, whichever comes first. 1A Auto aftermarket catalytic converters will also save you up to 30-50% over new OEM replacement parts. We also provide a line of universal catalytic converter replacements in addition to direct fit catalytic converters for those looking for a custom application.
