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Symptoms of a Bad or Failing Muffler


Did you know that the first internal combustion engine had a muffler installed? Although it wasn't up to today's standards, nor was it designed to reduce emissions or sound, the first combustion engine developed by J. J. Étienne Lenoi in 1859 had a small metal reducer on the end of the exhaust designed to reduce backfiring. Since those early days, mufflers have evolved and have become required components on any vehicle that operates on roads in the United States.

Today's mufflers serve two functions:

  • To reduce exhaust system noise that is directed from exhaust ports to the exhaust pipes
  • To help direct exhaust gases out of the engine

A common misconception is that mufflers are also an important part of vehicle emissions. Although there are chambers located inside the muffler that help to break up particulate matter emissions, the emissions control is the duty of catalytic converters; which are installed prior to the rear muffler and can reduce dangerous chemical emissions coming from the rear of today's combustion engines. When mufflers become worn out, they typically lose their ability to effectively "muffle" the sound of the vehicle's exhaust.

Mufflers typically last five to seven years on most US vehicles, but can become worn out prematurely due to several issues including:

  • Being exposed to salt; either on roads that are commonly iced or snowy or saltwater in communities near oceans.
  • Being frequently hit due to speed bumps, low clearance pot holes, or other impact items.
  • Excessive use or custom fabrication that is not recommended by the manufacturer.

Regardless of the precise cause, broken mufflers typically exhibit a few common symptoms that will alert the vehicle's owner that a problem exists and needs to be repaired or replaced by an ASE certified technician. Noted below are a few of the warning signs of a broken, bad, or failing muffler that should be replaced.

1. Engine is misfiring

Today's engines are finely tuned machines, where all components must work together in conjunction in order to work effectively and efficiently. One of these systems is the vehicle's exhaust which begins at the exhaust valve chamber inside the cylinder head, flows to the exhaust headers, into the exhaust pipes, then to the catalytic converter, to the muffler, and out the exhaust pipe. When any of these components are damaged, it can impact vehicle performance, including causing engine misfiring. If the muffler has a hole inside the unit and loses its efficiency, it can cause misfiring in the engine, particularly when under deceleration.

2. Exhaust is louder than normal

Loud exhaust noise is usually the result of an exhaust leak that commonly occurs in the muffler as opposed to the exhaust components located near the engine. As engine exhaust flows through the exhaust system, it is contained and eventually flows through the muffler. Inside the muffler is a series of chambers that helps to reduce the vibrations coming through the exhaust which is commonly associated with sound. When the muffler is damaged or has a hole in it, this causes the pre-muffled exhaust to leak, increasing the sound that comes out of the exhaust system.

Although it is possible that exhaust leaks can occur before the muffler, in most cases, loud exhaust is caused by a leak in the muffler itself. In either case, a certified mechanic will need to inspect and repair this issue.

3. Condensation from the exhaust pipes

When the exhaust system, including the muffler, cools down from the engine being run, the moisture in the air condenses inside the exhaust pipe and the muffler. This moisture sits there and slowly eats away at the exhaust pipe and the shell of the muffler. Over time and countless warm up/cool down cycles, the exhaust pipe and the seams of your muffler rust out and start to leak exhaust gases and noise. When you notice excessive condensation coming from the exhaust pipe, especially in mid-day or warmer periods of the day, this may be a signal that the muffler is starting to wear out.

As the muffler is a critical component of the complete operation of your vehicle, any of the above warning signs should be taken seriously and inspire you to contact a local ASE certified mechanics as soon as possible.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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