While a catalytic converter is designed to last 10 years or more, several variables can make it die sooner. Nowadays, vehicles employ more than one converter, which increases the chances of internal or external problems. When catalytic converters were integrated for emissions control, they converted harmful hydrocarbons and carbon monoxide into cleaner emissions. Three-way converters are now used to additionally control and convert nitrogen oxides. Oxygen sensors now monitor the efficiency of each converter on every vehicle.
The External Converter
The external shell and attachments of the catalytic converter is relatively simple to monitor. If damage occurs to the external components, the exhaust will leak from the compromised shell and emit a loud noise. Premature damage to the converter can occur from undercarriage incidents. Also pipe connections or flange connections are common areas that deteriorate from age and existing in hostile environments. Not only will the noise alert the driver that there is a problem with the converter, but performance issues can arise from an external exhaust leak from the catalytic converter. Lower exhaust back pressure can cause engine performance problems as well as trigger the oxygen sensor monitoring the converter to misread the information it's designed for.
The Internal Converter
The average temperature an exhaust system operates under is 1,93.3 to 871 degrees Celsius. The internal structure of the converter is made of platinum and palladium honeycomb that filters and chemically alters the exhaust emissions. As pollutants increase in the exhaust, so does the operating temperature of the internal structure. At 0-16.667 degrees Celsius, the structure will begin to weaken or melt, reducing its efficiency to convert harmful gases into less harmful pollutants. The platinum and palladium honeycomb will begin to melt into the ceramic substrate. When this occurs, the structure can break down or clog the converter, which results in little to no back pressure flow through the converter.
The oxygen sensor will fail to register the efficiency of the converter and transmit the communication to the computer of the vehicle. In addition, little to no back pressure will result in a poor-performing engine. When exhaust is prohibited from exiting the combustion engine properly, it will choke on its own exhaust or stop altogether.
Rarely does a converter break down internally on its own. Replacing a clogged or compromised converter may simply mean placing a bandage on a gaping wound. Exhaust from a combustion engine expels and recirculates unburned fuel and oxygen necessary to allow the engine to operate properly. A perfect fuel-to-air ratio exists for a combustion engine to function, and when that ratio is compromised, other components in the engine and exhaust system can and will fail.
Unburned fuel is a leading contributor to causing a catalytic converter to fail internally. So replacing the converter only temporarily solves the problem. When the engine is not performing as it should, it's only a matter of time before it damages the new converter. Diagnose any and all diagnostic trouble codes before replacing a catalytic converter to preserve and enhance its performance and effectiveness.