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Exhaust + Emissions Service & Maintenance | Parts of Car Emissions | Air Check Texas 

What components make up the Exhaust System?

  • Catalytic Converter: To reduce the levels of unwanted gasses exiting the engine through the tailpipe, vehicles are fitted with catalytic converters in their exhaust system. The Catalytic Converter [often referred to as the Cat] contains honeycomb structure that is coated with a catalyst such as platinum or palladium. When the catalyst becomes hot, the chemical structure of the exhaust gasses passing over it will change. Nitrogen Oxides are broken apart and the nitrogen exits the tailpipe. The oxygen that is split from the nitrogen combines with poisonous carbon monoxide to create carbon dioxide, and any unburnt fuel [or hydrocarbons] also combine with oxygen to make more carbon monoxide and water. When too much unburnt fuel reaches the catalytic converter, as a result of a poor running engine, the catalyst can be damaged and may need to be replaced. When the engine is running in such a way that the Cat may be damaged, the check engine light should come on.
  • Exhaust Hanger: To prevent the excessive noise and vibration that would occur if the exhaust were bolted directly to the vehicle body, exhaust systems are suspended under the vehicle on thick rubber loops. When the hanger loops become stretched or broken, the exhaust may not hang in the correct position, which can result in rattling or banging under the vehicle. Exhaust that becomes badly misaligned may push against plastic bumpers causing the bumpers to melt.
  • Exhaust Manifold: The exhaust manifold is bolted to the side of the cylinder head, and has tubes through which the exhaust gasses from each cylinder travel. The individual tubes are then combined into a bigger single exhaust pipe. Between the cylinder head and exhaust, there is a gasket that seals the two parts together to prevent leaks. Exhaust leaks in the area of the manifold may be a result of a leaking gasket, or could be a result of a cracked exhaust manifold. These leaks are often louder when the engine is first started and become quieter as the parts heat up and expand. Exhaust leaks that can get into the cabin of the vehicle should be replaced as soon as possible.
  • Flex Pipe: Because the engine tilts slightly under acceleration and braking, a flex pipe is inserted near the front of the exhaust so that the engine movements do not force the entire exhaust system to move also. The flex pipe normally has a steel hose like a drier hose wrapped in a protective steel braid. Damaged motor mounts that results in excessive engine movement can result in damage to the flex pipe.
  • Muffler/Silencer/Tailpipe: The muffler is normally located at the back of the exhaust system and as its name suggest, reduces the amount of noise coming out of the exhaust. As the sound waves from the engine travel down the exhaust pipe, the waves are bounced back inside the muffler to collide with the incoming sound waves, cancelling out some noise.
  • PCV Valve: Controls internal pressure in the engine
  • EGR Valve: Recirculates some of the engine's gas back into the intake manifold to be reburned, thereby reducing emissions.
  • Oxygen Sensor: Senses oxygen content in the exhaust gas. The Powertrain Control Module (PCM) uses this input to optimize the combustion process.

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