Defective exhaust? This is to be done when there is booming and noise!

Reading time 11 Min.

Recently updated on January 27, 2022 at 10:19 am

Do you notice that the volume of your car increases (significantly) from time to time? And all of this without a deliberate change like with one Sports exhaust system or one Air Intake System? Then the exhaust is usually the reason. For many, this may sound like bad news at first, but the construction of an exhaust system is usually relatively simple and the materials used are often quite cheap. Of course, always depending on the vehicle type. But a so-called bread-and-butter car is not necessarily demanding. This makes the installation easier, more precisely, the change of the exhaust on your own, which is why this can often be done without major problems even as a layman. However, there are a few tips that you need to keep in mind. In this article, we would like to introduce you to what these are.

Defective exhaust? That is to be done!

Who is only interested in very specific areas around the topic Defective exhaust? That is to be done! interested, you can use the following jump labels to navigate directly to the desired topic with just one click. And just as quickly you can return to this overview from the selected menu item with just one click. However, we recommend our readers to always read the entire article. Some menu items are only really comprehensible and understandable once the complete information article has been read.

1. The components of the exhaust
2. What does the elbow do?
3. How long does the elbow last?
4. Where is the downpipe installed?
5. Where is the flex pipe / flex piece installed?
6. Where is the catalytic converter installed?
7. Where is the exhaust pipe installed?
8. Where are the rear silencer and tailpipe installed?
9. What are the retaining rubbers on the exhaust system for?
10. What are the weak points of the exhaust?
11. Are there any other weak points on the exhaust!
12. Defective exhaust? Half so wild!
13. Which exhaust parts cost little?
14. The repair of the exhaust system!
15. Exhaust welding? Usually pointless!
16. Replacement of the complete exhaust system
17. Sports exhaust system as an alternative!
18. Exhaust system changer tutorials!
19. summary information on the exhaust system

The components of the exhaust

There are various components in the exhaust that the exhaust gas flow passes through. This is the elbowwhich Y-pipewhich Flexible pipe, the Catalyst, the central pipe, the middle silencer, the rear silencer and finally that End piece. Back to overview

What does the elbow do?

As everyone knows, exhaust gas is always produced when combustion takes place in the engine. This exhaust gas enters the manifold through the exhaust valve, which is located on the manifold seal. As the name suggests, the manifold is a curved pipe that is responsible for conveying the hot exhaust gases under the vehicle. The manifold is subject to strong vibrations because it is located directly under the engine. In order to be able to withstand these vibrations, the manifold is relatively heavy and massive and is usually made of cast iron. Back to overview

How long does the elbow last?

The manifold normally lasts as long as the vehicle itself. An exception to this is if the engine is unbalanced, for example. In this case, cracks may appear in the manifold. But also due to age, the manifold can break due to material fatigue after a high mileage. The manifold is one of the most expensive components of the exhaust, but this does not mean that replacing the manifold is necessarily particularly difficult. An exception to this is when the catalytic converter is integrated in the manifold, which is the case with some vehicles. Back to overview

Where is the downpipe installed?

The so-called Y-pipe is connected to the bend. The task of this Y-pipe is to combine the exhaust gases flowing out of the combustion chambers into a single exhaust pipe. The Y-pipe is also usually a fairly massive component. There is also the in the manifold Lambda probewhich is there to check the oxygen content in the exhaust gas and ensures that this information is passed on to the control unit. Back to overview

Where is the flex pipe / flex piece installed?

The so-called flexible pipe is located behind the Y-pipe. In contrast to the elbow or the Y-pipe, this is by no means a massive component. The flexible tube made of stainless steel is only a few centimeters long and, thanks to the wire mesh, is very flexible and can be turned and bent in any direction. This is due to the task of the flexible pipe: It conducts the already mentioned vibrations of the motor CAN'T to the following components of the exhaust. Back to overview

Where is the catalytic converter installed?

The catalyst sits behind the flexible pipe. Simply put, the job of the catalytic converter is to purify the exhaust gases. Decoupling from the strong vibrations is important for the catalytic converter, since the inside of the catalytic converter is made of ceramic, which could easily be broken by the strong vibrations. By the way, many vehicles have a so-called diagnostic probe installed after the catalytic converter. More information on this in the next paragraph. Back to overview

Where is the exhaust pipe installed?

The actual exhaust pipe comes after the catalytic converter. In some cases this pipe still has a center silencer. Since 2014, many new cars have had an additional probe in the center tube, the so-called diagnostic probe, which is used to check the catalytic converter for proper function. Back to overview

Where are the rear silencer and tailpipe installed?

Behind the center pipe is the rear silencer, which has the task of reducing the noise produced by the engine as best as possible. The actual tailpipe is connected to the rear silencer. The attachment of the exhaust to the underbody of the vehicle is ensured by simple but robust retaining rubbers. Back to overview

What are the retaining rubbers on the exhaust system for?

The retaining rubbers on the exhaust system are installed for a constant distance between the exhaust and the floor. In addition, these retaining rubbers are there to enable an oscillating movement so that the solid tubular body does not bend. And the rubber mounts ensure that vibrations from the engine and vehicle are only minimally transmitted to the exhaust system. The rubbers become brittle over time but can be easily replaced. It becomes more difficult if the bracket for the rubber on the vehicle or on the exhaust has rusted away. Back to overview

What are the weak points of the exhaust?

The flexible pipe is the component of the exhaust that is exposed to the greatest stress. This is because it has to be resistant to high temperature fluctuations and is beaten all the time. Although the price for the flexible tube for simple vehicles is only around 15 to 50 euros, it is extremely robust. But if it shows a defect, this is noticeable in an extremely high level of noise. Even a 1-liter VW Polo sounds like a powerful sports car at first sight. Back to overview

Are there any other weak points on the exhaust!

Other weak points are the rear silencer and the catalytic converter. The mixing of soot and moisture in the rear silencer can cause an acidic liquid to form, which over time “eats” its way through the exhaust. This is also noticeable relatively quickly due to the increased volume. If the catalytic converter is defective, a rattling or rumbling can be heard, which is caused by broken ceramic bodies. To do this, the engine control lamp is often activated because the catalytic converter can no longer properly clean the exhaust gases. Reduced engine performance can also be a symptom. Back to overview

Defective exhaust? Half so wild!

As mentioned earlier, repairing the exhaust on a simple vehicle is relatively simple. What does vary, however, are the prices of the individual components of the exhaust. The catalyst is almost always the most expensive part, which can easily cost 1000 euros. True is a used catalyst a plausible alternative, but you can never really be sure about the condition here. Another expensive component is the manifold. Here, too, the prices fluctuate enormously and in the case of two built-in exhaust manifolds the costs are double. The same applies, of course, to two catalysts. For current vehicles such as a BMW 5 Series, Audi A6 & Co., changing parts or the entire exhaust system yourself is not recommended. Although this is also possible, the process is often more difficult and, above all, more expensive than a VW Golf V or an Opel Astra. It is also possible that special tools are required that are not available in a private household. Back to overview

Which exhaust parts cost little?

The rear silencer is a cheaper component. Depending on the model used and the driving style, this can already show a defect after a few years. Usually such a rear silencer costs well under 100 euros - just like the center silencer. The central pipe is usually extremely robust, but the durability does not come close to that of the elbow or the Y-pipe. The cheapest component of the exhaust system is usually the tailpipe and of course the simple rubber mounts. Back to overview

The repair of the exhaust system!

In simple vehicles, the exhaust system consists of several pipes inserted into one another, which are held together by clamps. Although these can be solved theoretically, they can get stuck, which makes it much more difficult to loosen. In such a case, mostly only the flex or strong heating are the way out. Here, however, the spark beam should lead away from the vehicle and attention should also be paid to the increased risk of fire. Some vehicles have exhaust systems that consist of fewer individual parts. Then the repair is of course more expensive and a replacement is usually more complex. The layman can quickly reach their limits here. And there are even vehicles where the exhaust system is almost in one piece. Then the exchange by the layman is almost impossible. An alternative are spare parts that are used with a flange at the front and rear at the defective point. But even this variant is sometimes very complex. Back to overview

Exhaust welding? Usually pointless!

What doesn't make any sense, however, is welding the exhaust. This is because the sheet metal can hardly be welded properly due to its thickness. Instead, replace the entire ESD here and don't waste your time on welding. For example, if the rear muffler is rusted through in one place, it can perhaps be repaired by means of makeshift welding work, but the rest of the muffler should also be attacked. Back to overview

Replacement of the complete exhaust system

Another alternative is to replace the entire exhaust system, which is easier in practice. Another advantage is the increased service life and safety. Plus, you don't have to worry about the other components that could break soon after replacing a single part. Without a catalytic converter, you can get such exhaust systems completely for less than 100 euros. Back to overview

Sports exhaust system as an alternative!

An alternative is of course a high-quality sports exhaust system. Of course, this is significantly more expensive but also has many advantages. Sports exhaust systems are almost always made of stainless steel and are therefore extremely durable. In addition, you can cause a slight increase in engine performance and of course an improved exhaust sound. The vehicle, the area of ​​application and the personal taste with regard to the desired "acoustics" are always dependent. Back to overview

Exhaust system changer tutorials!

The following videos show you tutorials for changing various components of the exhaust system. A change of the complete exhaust system is also included. Back to overview

summary information on the exhaust system:

• The exhaust system (colloquially also exhaust) is responsible for discharging the exhaust gases from the engine
• The main components are the manifold, Y-pipe, catalytic converter and silencer
• can Ingredients: of the system are used to reduce the pollutant content in the exhaust gas and for noise insulation/damping
• typical symptoms of a defect
  - rusted spots, holes, cracks (mostly on the rear silencer)
  – Check engine light comes on / flashes
  – Drone while driving (usually when accelerating)
  – The vehicle is significantly louder while driving
  – limited performance above a certain speed
  – Increased fuel consumption
  - Error memory entry ("Catalytic converter efficiency insufficient", "Catalytic converter flow rate too low", "Particulate filter differential pressure deviation" etc.)
  - tinny clang
  – Problems with the emissions test
• the symptoms mentioned not all together occur, but can also occur individually
• Effects: defective exhaust system for the main inspection
  - If the exhaust system is defective, the exhaust gas test will not be passed
• Continue driving with a defective exhaust system?
  Depending on the type of defect, this may be possible, but a workshop should always be consulted as soon as possible
  - if the vehicle continues to be used without repairs, this is an unnecessary environmental and noise pollution (can result in a fine)
• Repair/replacement of parts of the exhaust system
  - often only a part of the exhaust system has to be repaired or replaced (often the rear silencer/muffler)
  - Defects in the suspension of the exhaust system are generally inexpensive
  – Flex piece or holder can often be welded
  – a defective muffler should be replaced with a new part (welding can work as a workaround)
• the cost of changing a muffler varies widely
  - Silencer (front silencer, middle silencer, rear silencer)
  – Rear silencer usually costs between 100 and 1.000 euros. (Front and middle silencers are usually cheaper)
  – the change usually takes between 30 and 120 minutes.
• the cost of changing the flex pipe varies greatly
  – Material costs are between 30 and 400 euros
  - Workload around one to one and a half hours
• the cost of changing the manifold varies greatly
  – Material costs for an exhaust manifold are around 50 to 400 euros
  - Manifold and catalytic converter as a combined component can cost up to 1.000 euros
  – Duration for the change between 30 minutes and four hours
• the cost of changing the catalytic converter varies widely
  – Material costs are between 300 and 1.000 euros
  – Exchange usually takes one to three hours
• Structure of a typical exhaust system (differs depending on the vehicle and engine type)
  then the "gasoline" or Otto engine
  – the exhaust manifold
  - Possibly exhaust gas turbocharger
  – the flex pipe
  – the pre-cat probe (also called control probe)
  – the catalyst
  – the post-cat probe (also called monitor probe)
  – the front silencer
  – the middle silencer
  – the rear silencer
  follow the diesel engine
  – exhaust manifold
  - possibly exhaust gas turbocharger
  – Flex pipe
  – Sensor for exhaust gas pressure and temperature
  – Particulate filter
  - If necessary, SCR catalytic converter
  – front silencer
  – middle silencer
  – rear silencer
• Back to overview

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