Key Takeaways
The following are the key takeaways from this article:
- The exhaust manifold comprises multiple pipes collecting exhaust gases from the cylinders and directing them to a single pipe.
- A car’s exhaust system comprises a manifold, flex pipe, oxygen sensors, catalytic converter, heat shield, and muffler assemblies.
- The common problems with an exhaust manifold can be damaged exhaust manifolds, leakage in the gaskets, and loosened bolts.
- The symptoms of a bad exhaust manifold include unusual engine sound, bad fuel economy, odd-smelling exhaust gas, lack of acceleration, and check engine light.
- The cost to resolve exhaust problems can vary from $20 up to $2500.
Introduction
Exhaust gases comprise harmful fumes of carbon dioxide, nitrogen, Sulphur, etc., that are harmful to the engine and passengers.
Auto-manufacturers have thus designed an exhaust manifold to collect gases from the engine cylinder and direct them towards the exhaust pipe.
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Each cylinder has individual exhaust headers that are converged into a single tube called a collector (1). Although a standard exhaust manifold is installed in the engine, the drivers can install aftermarket manifolds known as headers to enhance the engine performance. The history, function, parts, and common problems of exhaust manifolds are further discussed in this article.
History of Exhaust Manifold
The exhaust manifold is an important part of the engine system. Its purpose is to gather all the exhaust gases from the cylinders of the engine block and then transfer them to the catalytic converter. It is considered the first section of the exhaust system of the vehicle. The exhaust manifold was first time invented in 1960 in the USA by Headers (1).
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This part was designed when scientists observed the release of harmful gases from the vehicle’s tailpipe. Also, after the Second World War, the ratio of harmful gases increased greatly, and releasing harmful gases from vehicles increased pollution.
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Therefore, the exhaust manifold was designed. This part treats the harmful chemicals before releasing them into the environment. After the invention of this part, the first experiment was performed in the passenger car in 1963. Later in 1968, a modification was made to the exhaust manifold. This part also treated the nitrogen and carbon oxides before releasing the waste product into the environment. Later, the purpose of this part remains the same, but continuous amendments are being made with the advancement in technology.
The function of the Exhaust Manifold
With the latest technology, the hardware part of the exhaust manifold is then further connected to the vehicle’s computer system. This part helps detect the waste material’s harmful chemicals before releasing them into the environment. Initially, this part was made of iron, but now steel is used to manufacture the exhaust manifold. This is because iron is heavy and gets rusted immediately (1). The steel has long and durable life and is light in weight. The main function of this part is to gather all the vapors and gaseous fumes from multiple cylinders and then send them toward the catalytic converter. Moreover, it prevents the fumes from entering different cylinders. Also, it helps build the right amount of pressure in the engine and maintains the rpm.
This part is very beneficial as it immediately removes all the harmful chemicals and waste products from the combustion chamber and lets the fresh air enter it.
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As a result, a large amount of power is generated in the vehicle. Thus, this part plays a vital role in maintaining the good health of the engine (1).
Parts of the Exhaust System of the Engine
Following are a few important parts of an exhaust manifold:
Manifold
A manifold is the most important part of an engine’s exhaust system. The purpose of a manifold is to collect the exhaust gases from all engine cylinders and direct them toward the exhaust pipe.
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The tubes of a manifold can vary depending on the engine’s cylinders. Generally, larger engines have more cylinders, so the manifold pipes, in this case, would be greater (1). Manifold is manufactured from cast iron, and a manifold’s width is kept to incorporate a catalytic converter. It is further connected to the engine at exhaust ports with the help of flange connectors.
Flex Pipe
Flex pipes are designed to alleviate any engine damage from the exhaust system. It is a stainless steel/cast iron pipe that allows for flexibility to the exhaust line during vehicle movement.
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A rigid pipe can experience cracks during vehicle movement if it is stationary, so a flex pipe is designed to prevent damage to the exhaust system and engine during vehicle movement (2).
Oxygen Sensors
Oxygen sensors can be placed inside the manifold, which are simple sensors used to collect information about exhaust gases.
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These sensors, as the name indicates, analyze the oxygen content in the exhaust gas. So, this information can be sent to the PCM that controls the fuel and monitor the engine efficiency (1).
Catalytic Converter
A catalytic convertor uses a catalyst to convert harmful components of exhaust gases, such as Sulphur, carbon dioxide, etc., into less harmful components like steam. It is designed to split the molecules of unsafe gases before being released into the air. In some car models, the catalyst is placed inside the manifold, while in some models, the catalyst is placed inside the exhaust pipe (4).
Heat Shield
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Heat shield prevents hot exhaust gases from directly entering the manifold.
It also functions to avoid cylinder overheating.
Muffler Assemblies
Muffler assemblies are designed to alleviate the engine voice when the exhaust gases pass out of the exhaust system. The muffler is further attached to the exhaust pipe of the vehicle.
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The drivers can also install aftermarket muffler assemblies to enhance or decrease engine noise (2).
Common Problems of an Exhaust Manifold
Damage Exhaust Manifolds
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The major problem in the exhaust manifold is the crack in the body. Due to the cracks in the exhaust manifold, the exhaust system’s performance is affected, and all the harmful gases in the multiple cylinders are not well treated. As a result, harmful gases are released into the environment.
The exhaust manifold gets damaged due to the metal crack, and as a result, the noises are observed in the engine system. Moreover, the black-colored smog is also released from the tailpipe as the nitrogen and carbon oxides are not broken down into the components and usually remain inside the cylinders. As a result, a thick layer of fumes is deposited over the walls of cylinders and the combustion chamber (2). Thus, the exhaust gases have a rotten egg smell. This completely damages the engine’s performance and it becomes rough and idle.
Leakage in Gaskets
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Gaskets are an important part of the engine, but a fault in the gasket can damage the exhaust manifold system.
The gaskets can get damaged due to high pressure, temperature, and excessive vibrations. This constant friction and high pressure then cause leakage in the exhaust manifold. This issue can lead to engine failure. Besides, the dirt and debris in the exhaust manifold can impact its performance. This is because the dirt particles can create blockage in the pipes, and as a result, the fumes may face hindrances while released. This causes an issue for the engine as the air is then not released from the combustion chamber. This does not allow fresh air to enter the combustion chamber. As a result, the oxygen content is reduced, and the maximum pressure is not generated. Thus, the car fails to accelerate at high speed, and multiple variations will be produced in the engine.
Loosened Bolts
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Loosened bolts and nuts are considered one of the major reasons for exhaust manifold failure. Due to the loosed or over-tightened bolts, the pressure can increase and ultimately damage the manifold body.
This damage causes leakage, and the exhaust system’s performance gets damaged (2). The engine check light is illuminated to indicate the error. The harmful gases then keep on accumulating within the engine, and this results in poor performance of the engine. The engine starts consuming more fuel, and thus the harmful gases are deposited on the walls of the engine, hampering the engine’s health.
Symptoms of a Bad Exhaust Manifold
Following are a few symptoms of a bad exhaust manifold:
Unusual Engine Sound
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If your engine is making unusual sounds or sounding louder than normal, it could be a sign of manifold mulfunctioning.
Usually, the engine becomes louder when the manifold is damaged, and the exhaust gases leak. However, there can be a chance that some other exhaust component is malfunctioning, resulting in unusual engine sound (3). You can check the OBDII code, in this case, to detect which component is malfunctioning exactly.
Bad Fuel Economy
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A damaged exhaust manifold can also result in bad fuel economy. In this case, the leaking exhaust gases will impact the reading of the oxygen sensors.
When oxygen sensors send wrong information to PCM, it can inject more fuel into the engine (3). So, if you need more trips to the gas station lately, it can be due to a bad exhaust manifold.
Odd Smelling Exhaust Gas
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Another sign of a bad exhaust manifold can be a foul smell under the hood or from the exhaust pipe. It is because the exhaust gases could leak before entering the exhaust system, converting them into different molecules.
The exhaust gas is more harmful in this case and would smell odd compared to the normal exhaust gas (4). So, if your hood smells odd or your passenger compartment smells like fuel, there is a chance that the exhaust manifold is damaged.
Lack of Acceleration
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A bad exhaust manifold can be one of them, where lack of acceleration can be due to several other engine problems.
As discussed, a leak in exhaust gases can impact oxygen sensor readings. So, the PCM can get the wrong information and send more or less fuel to the engine impacting the acceleration (5). Lack of acceleration is thus an alarming sign that should not be ignored.
Check Engine Light On
The final symptom of a bad exhaust manifold is the check engine light. The check engine light indicates that some engine component is malfunctioning. You can always connect a hand-code reader with the OBDII module to further check the engine fault code (5). This code can be decoded using online platforms to analyze the particular problem in the engine further.
Conclusion
To conclude, it can be said that the exhaust manifold is a small yet important part of the engine that collects exhaust gases from cylinders and directs them to the exhaust system. This part comprises multiple pipes connecting each cylinder of the engine. Generally, cast iron is used to manufacture exhaust manifolds, but aluminum alloys can also be used to manufacture them. The common signs of a bad exhaust manifold are unusual engine sound, bad fuel economy, odd-smelling exhaust gases, lack of acceleration, and blinking of the check engine light. A driver should resolve the exhaust manifold issues at the earliest to avoid any further engine damage.
FAQs
Exhaust leaks can cause a lack of engine power. Also, the oxygen sensor sends wrong information to the PCM impacting the engine performance. Besides leaks, the cracks in the manifold can allow air to enter the engine, resulting in engine stalling. This can blow the head gasket or overheat the head, impacting the engine. So, the exhaust manifold issues should be resolved at the earliest.
Usually, the exhaust manifold issue can be resolved for $200-300, depending on the car’s model. The labor will cost around $100-200, depending on the labor hours required to resolve the issue.
Usually, the engine sound is increased when the exhaust manifold is leaking. Similarly, you might face a tapping or ticking sound. The tapping or ticking sound is more common when the engine starts, and the exhaust manifold is cold.
