Everything you need to know about car exhaust system

Aivaras Grigelevičius

Aivaras Grigelevičius

Some car components can be surprisingly complex despite their simple looks and functions. A prime example of this is the car exhaust system, which actually does a lot more than expected.

Let’s explore the crucial role of the car exhaust system and how you can effectively diagnose and identify potential issues.

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What does a car exhaust system do?

Since the beginning of combustion engines, the primary role of the exhaust pipe has been to gather gasses from the cylinders and release them into the air. Over time, technological developments have transformed exhaust pipes into exhaust systems that are designed to meet a series of requirements.

In today’s world, exhaust systems have the task of eliminating harmful substances and reducing CO2 emissions. Additionally, they must also comply with noise pollution regulations while ensuring smooth engine performance.

Car exhaust system – the 4 main parts

exhaust system
Source: Oscar Sutton / Unsplash / Exhaust system

The exhaust system in modern automobiles consists of various components that are typically visible only when the car is placed onto a lifter. To spare you the trouble, let’s examine each component individually.

1. Tail pipe(s)

The tail pipe is the last component of the exhaust system – you may notice looking at the back of the vehicle. The number of tail pipes usually ranges from one to three, depending on the specific vehicle.

Tail pipes act as outlets through which exhaust gasses are efficiently expelled into the open air.

2. Oxygen sensor

The oxygen sensor, also referred to as an O2 sensor or lambda sensor, is a device designed to measure the oxygen levels in the exhaust emissions of an internal combustion engine. 

Its primary function is to generate a voltage signal that accurately reflects the amount of oxygen present in the exhaust gas. This signal is then sent to the engine control module, which utilizes the information to finely adjust the air/fuel mixture for optimal combustion and to minimize emissions.

3. Catalytic converter

The catalytic converter is a crucial and one of the most expensive parts of the exhaust system.

Usually, it’s connected to the exhaust pipe, although it can also be a smaller component located directly within the exhaust manifold. Regardless of the design, it comprises a metal housing and a catalytic core, which can be made of metal or ceramic materials.

The core consists of small channels coated with precious metals like palladium or platinum. These metals serve a critical function in the chemical process of breaking down harmful substances present in exhaust gasses, such as nitrogen or carbon oxides, and transforming them into harmless carbon dioxide and water.

4. Muffler

The primary purpose of a muffler is to minimize the noise produced by the exhaust system. 

Depending on legal regulations, muffler manufacturers use various silencer types to reduce both noise and vibrations. These include reactive silencers, resistive silencers, absorptive silencers, and shell damping systems.

Modern mufflers have also become a subject of interest for car enthusiasts. Petrolheads seek to enhance or alter the sound of the exhaust system, prompting them to modify, replace, or even eliminate the muffler altogether.

Exhaust issue symptoms and what they mean

amg tailpipe
Source: Mazuozi Abdeladim / Unsplash / AMG tailpipe

You don’t always have to visit the nearest workshop to address or diagnose certain issues with your exhaust system. If you suspect a fault in your car’s exhaust system, be on the lookout for the following symptoms.

Unusual noises

The most noticeable sign of a malfunctioning exhaust system is an increased or unusual engine sound. For the most part, these sounds originate from three different sources: the exhaust manifold, muffler, or exhaust pipe.

Exhaust manifold issues

  • Cause. Over time, the development of cracks between the cylinder branches, failure of studs and bolts due to thermal cycling, and warping of the manifold surface can result in gasket failure. Additionally, there could be a sensor issue since it is housed within the exhaust manifold.
  • Other symptoms. A leaking or cracked exhaust manifold causes a burning smell from the engine bay, and depending on the extent of the issue, it may result in decreased engine performance and increased fuel consumption.

Muffler issues

  • Cause. Due to its specific function, muffler issues are typically caused by the vulnerability to corrosion.
  • Noise description. As corrosion progresses slowly, early muffler issues start with hissing or popping sounds. In later stages, a failing muffler produces louder noises, noticeable even at idle engine speeds.

Exhaust pipe issues

  • Cause. Like the muffler, exhaust pipes can rust over time from exposure to heat, moisture, and road salt, impacting both the pipes and their connections.
  • Other symptoms. In addition to increased engine sounds and strange knocking sounds (as insecure connections allow pipes to move or vibrate), rust may result in noticeable smells.

Reduced engine performance

A faulty fuel system or bad ignition components are typical culprits of reduced engine responsiveness, but parts like the exhaust gas recirculation valve or oxygen sensors can also significantly impact engine performance.

Exhaust gas recirculation valve issues

  • Cause. Issues with EGR valves arise from accumulation of carbon deposits, resulting in clogging and restricted functionality of the valve.
  • Symptoms. The most noticeable indication of an EGR valve issue is rough engine idling and a decline in fuel efficiency, as the valve struggles to adequately recirculate exhaust gasses back to the engine.

Oxygen sensor issues

  • Cause. Natural wear and corrosion are the main reasons why oxygen sensors start malfunctioning. 
  • Symptoms. As these sensors monitor oxygen levels in the vehicle’s exhaust gasses, any disruption in communication between at least one oxygen sensor and the engine control unit could result in engine misfiring, rough idling, or even stalling. Additionally, a rich air-to-fuel mixture may lead to exhaust system smoke.

Emission control system issues can cause a range of symptoms

The catalytic converter and particulate filter are crucial components in reducing harmful emissions. Potential issues with these components will impact your overall driving experience.

Particulate filter issues

  • Cause. Problems with the particulate filter arise from different sources: a defective EGR valve, the use of incorrect oil, and defective fuel injectors. Additionally, short trips can have a significant impact on the clogging of particulate filter, as the engine can’t reach optimal operating temperature.
  • Symptoms. When particulate filter become clogged, an amber warning light will appear on the dashboard, signaling the need for automatic particulate filter system regeneration. This can be achieved by driving on the motorway at a steady 70 mph. If necessary, consult a workshop that can initiate static regeneration.

Catalytic converter issues

  • Cause. Catalytic converter failures often result from overheating, oil slipping into the exhaust, or structural damage. The good news is that early catalytic converter failures could be reduced by being proactive in vehicle maintenance. For example, faulty oxygen sensors can push the converter to operate at unusually high temperatures, significantly reducing its lifespan. 
  • Symptoms. A malfunctioning catalytic converter often forms a chain of events, beginning with an illuminated check engine light, progressing to reduced engine performance, increased emissions, and noticeable change in fuel economy.

Importance of a healthy exhaust system

Toyota MR2 with modified exhaust system
Source: Jospeh Greve / Unsplash / Toyota MR2 with modified exhaust system

If there’s one thing everyone simply can’t overlook, it’s the condition of the exhaust system. If one early morning you start the engine, and your ears are greeted by strange noises and unpleasant smells, it’s safe to say you won’t be receiving any compliments from other road users.

However, the importance of maintaining your vehicle’s exhaust system extends beyond avoiding additional noise and discomfort. A well-maintained system plays a crucial role in ensuring optimal engine performance and, equally importantly, contributes to environmental preservation by minimizing harmful emissions. And if you want to stay on top of your vehicle’s health, consider using a VIN decoder.

A VIN decoder is a valuable tool not only for checking a vehicle’s history when searching for a new one but also for owners seeking additional information about specifications, recalls, or potential maintenance issues.

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Aivaras Grigelevičius

Article by

Aivaras Grigelevičius

Aivaras has been excited about cars since he was a little kid. Later, this passion for drivable objects (and everything that surrounds them) grew into work as an automotive journalist. Since then, Aivaras has written for several different magazines, covering anything with an accelerator pedal. He has a soft spot for cars with an Alfa Romeo badge.