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Driving our vehicles a day in and day out, we already know how it sounds. From the roar of the engine upon ignition to the quiet purr that it makes at idle, the sounds that we hear often give us peace of mind that everything is in order. As such, when we hear a sound or noise that we are not really familiar with, that was not there before, we often take it as a sign that there is something wrong with our car. And if it happens that you hear rattling noise from the rear, there’s a really great chance that you have an issue with your exhaust system; your muffler to be precise.

A Look at the Muffler

It is very easy to identify a vehicle with no muffler without really having to look under its body. It is definitely loud. You see, the idea of putting a muffler into the exhaust is to minimize the noise or sound waves created by the vehicle’s engine.

The sound or noise created by the engine is generally in the form of pressure waves of alternating low and high air pressures. A high-pressure wave is created by the engine every time the exhaust valves open. The molecules present in this high-pressure wave collide with the molecules in the low-pressure exhaust pipe. As the gas is propelled towards the end of the pipe, the sound waves travel a lot faster towards the tailpipe. This is why you will be able to hear the noise first before you can start noticing the gas coming out from the exhaust.

Now, your muffler is a simple but neat device that is placed just towards the tailpipe. Its job is to cancel out these pressure waves emanating from the engine so that you will not be able to hear them anymore. It does this in a process known as destructive interference. Remember what we said about noise being pressure waves? So, the very first pressure wave that hits the muffler is often the one with the highest pressure. However, the pressure wave following it is at the lowest pressure. When these waves reach the ear, they don’t register as noise simply because they cancel each other out.

Inside the muffler are tubes that are specially designed to produce pressure waves that are reflected and interfere with each other; thus, canceling each other out. When the sound waves and exhaust gases enter the center tube of the muffler they get bounced off and are exposed to air present in the resonator. This volume of air is what cancels out the sound waves coming from the engine. These are then reflected through the perforations found in the muffler’s main body before they leave towards another pipe with perforations. From here, they exit the muffler.

It should be noted that the muffler will only partially cancel the noise emanating from the engine; it doesn’t eliminate it completely. That is why they call it a ‘muffler’ because it muffles or softens the noise that we eventually hear.

Why the Muffler Rattles

Since the muffler is an integral component of the exhaust system and its location means it has to be connected to the exhaust pipe as well as to the underside of your car, the rattling sound that you may hear can come from any two possible sources. It’s either you have a loose muffler or misalignment in the exhaust system. Either way, this will always result in a rattling muffler.

Rattling noise coming from the rear of your car and right in the area where the muffler is located is often interpreted as a sign of a loose muffler. It is possible that your muffler came loose because of a bad connector, a loose or damaged bracket, or even a degraded rubber hanger. These components fix the muffler to the chassis of your car.

As you may already know, the muffler isn’t really plastic or rubber, to begin with. It is made up of metal. If the components that are supposed to keep it in place are not working properly, then the muffler will be moving up and down and sideways too as the vehicle moves along. Sometimes, you can even the rattling noise right after starting the engine and running it at idle. The rattling noise is typically heard while driving especially during acceleration or when you drive on poorly-paved roads. As the vehicle moves, the loose muffler gets hammered into the other parts of the car’s body producing the characteristic rattling sound.

The components that secure the muffler can get corroded over time. With corrosion comes weakness and this can lead to the loosening of the various connections. When it comes to corrosion, there are a lot of factors that can hasten the rate of corrosion. Things like road salt, excessive heat, debris, and even excessive moisture can all play significant roles in the oxidation of the metal.

It is also possible that the metal pipes inside the muffler itself are already damaged. Remember that the exhaust gas that is emitted by the engine can cause a variety of chemical reactions in these parts. This is especially true if you checked that the exterior connecting components of the muffler are intact.

One possible outcome of a loose muffler is a misalignment of the exhaust system. Think of it this way. The connectors on the muffler are primarily intended to keep it from moving. Once these are loose, the muffler will be moving in different directions which can further loosen the other connections. Unfortunately, the muffler is typically in line with the exhaust pipe which is connected to other parts of the system including the catalytic converter.

As the muffler moves violently creating the characteristic rattle, its movement also moves the different parts of the exhaust system. This can also loosen their connections and lead to a general misalignment in these components. In such cases, you are not only looking at a problem in your muffler but also a potential issue with other parts of your car’s exhaust system.

Looking for Signs and Symptoms of Muffler Damage

It is important to look for signs that indicate damage to your muffler. To do this, you will have to look under your car and visually inspect the pipe from the engine all the way to the tailpipe. Do not focus only on the muffler since, as we have already pointed out, loose connections can occur anywhere along the entire length of the exhaust pipe.

Try to look for signs of corrosion or rusting as well as loose connections, brackets, and hangers. Pay attention to the integrity of the muffler itself. Try to shake it. Ideally, it shouldn’t move. If it does, then you may have found a potential issue. Check the heat shield as well and try to determine if there are signs of damage.

You may also notice that you’re refueling a lot more frequently than you used to. One of the obvious benefits of having a fully functional vehicle exhaust system is fuel economy. If you have observed that your fuel economy has drastically decreased at about the same time that you first noticed the rattling sound, then there’s a good chance you have an issue with the muffler or your exhaust system.

Fixing the Rattling Muffler

You may think that the rattling noise coming from your muffler is something that you can live with for now. However, the more you delay in correcting the problem, the more serious it can get.

Fixing a rattling muffler can be as easy as tightening loose bolts or even replacing a bad or broken hanger. Unfortunately, if some of the parts of the muffler and exhaust system are already heavily corroded you will have no choice but to replace everything. This is something that’s best left to professionals.

If you are not sure what the real cause of the rattling noise is, it is best to bring your car to a mechanic. He will have to perform a variety of checks to make sure that the issue is something that can be easily fixed with a little tightening of loose bolts or perhaps even the replacement of connectors. And if the diagnosis indeed points to a problem with the muffler, then a more appropriate solution can be applied.

It is important to realize that the rattling sound you hear under your car may not come from the muffler itself. It can even come from the catalytic converter or the other components that make up the exhaust system of your car. Even the bolts and brackets that secure the tailpipe can become problematic over time. It is for this reason that a very thorough assessment of your car is required if you want to isolate the problem.

Muffler rattling may be a sign of a loose muffler or a seriously misaligned exhaust system. Whatever the case, the treatment for such a noisy problem is dependent on what causes it.

Sources:

  1. Signs of Problems with Your Car’s Muffler, Angie’s List
  2. Why is My Muffler Rattling?, Cars

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