Why Is My Muffler Rattling?

CARS.COM — Most exhaust problems can be diagnosed by paying attention to unfamiliar sounds or taking a look underneath the car. One of the most common exhaust problems is a rattling sound. When you hear a rattle, it could be caused by numerous things. Is your muffler rattling? If so, let's take a closer look at some of the possible causes and your repair options.

Related: What Are Common Exhaust System Problems?

What Causes a Muffler to Rattle?

In most cars, the muffler is installed in line with the exhaust pipe, and its job is to minimize the noise that comes from a car's engine. Mufflers contain perforated tubes or baffled chambers that create opposing sound waves when sound waves from the engine travel into the muffler. These opposing waves partially cancel out most of the original loud noise. In most areas, hitting the road with a missing or damaged muffler is illegal. This exhaust component is required by law to keep vehicles operating at acceptable noise levels. 

If you are hearing a loud sound like pieces of metal contacting each other, it usually means that something is touching the exhaust pipe. A loose bracket, rubber hanger or connector, or one that is badly corroded, can allow a muffler to rattle as the exhaust pipe bangs against another part of your vehicle when you accelerate or drive on bumpy roads, or even when you first start the car and it's stationary and idling. When the components that hold your exhaust together fail, they can cause misalignment in the system. When this happens, a rattling noise is common. If the rattling is caused by your muffler, it will most likely originate near the rear of your vehicle. 

A loose muffler can allow excessive movement in other components as well and increase the stress on those parts, so it can become more than an annoying noise if left unattended. If the muffler is hanging lower than normal, there's also a risk that it could be broken off by hitting a bump or going over railroad tracks. As a result, it is extremely important to repair muffler problems as quickly as possible. 

Signs of Muffler Damage

If you suspect that your car is making a loud noise due to a muffler problem, take a look at your exhaust system. While a loud rattling or rumbling sound is the most common sign, there are a few other things to check for. Get under your car and inspect the pipes that make up the exhaust. Do you see any rust or other damage? Pay close attention to the muffler itself and the heat shield. Are there any visible signs of damage? Also, pay attention to how your car is running. If you start to notice decreased efficiency, you could have an exhaust leak in a pipe or a damaged muffler. 

How to Fix a Muffler

Modern exhaust systems are usually made of aluminized steel or stainless steel, but that doesn't mean they or the parts that hold the exhaust components in place last forever. Heat, debris, road salt and moisture can all cause rust in the exhaust system. When you are having trouble with your car's exhaust, it's important to find a fix right away. These problems tend to get worse with time, and the longer you wait, the more it will cost to repair your vehicle. And loud noise isn't the only concern when you have a damaged exhaust: The rattle you hear may be annoying, but it could be a sign that the fumes from your vehicle's exhaust are not being routed away from your car properly. Exhaust leaks cause a rattle sound as well, and you could have exhaust fumes coming into your car from a damaged pipe. 

Though the loud sound of a muffler rattle might be fixed simply by tightening a couple of bolts or replacing a broken hanger, the corrosion might be bad enough on the muffler or neighboring parts that they will have to be replaced. Exhaust work is a big job, and unless you have the right training and experience, this type of repair is best left to the professionals. 

A rattle or banging noise from the exhaust system might not be an external problem. Baffles or other components inside of mufflers can come loose and cause internal rattles.

In addition, the muffler may not be the only cause or even the culprit. Brackets and bolts securing tailpipes, heat shields above catalytic converters and other components can come loose, and catalytic converters can develop internal rattles when they go bad.

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