A muffler is a major component of the exhaust system on a vehicle, intended to reduce engine noise. A vehicle will typically have one or two mufflers, depending on the configuration of both the engine and the exhaust system.
An internal combustion engine relies on rapidly expanding gasses produced by burning fuel to propel the pistons and produce power. The process of combustion, however, carries some unwanted byproducts in the form of harmful emissions, heat, and noise. Therefore, an engine is fitted with an exhaust system to route the engine exhaust away from vehicle occupants and to quiet down the sound of the engine.
The exhaust system collects the hot exhaust gasses in the exhaust manifold as they exit the engine’s cylinders. From there, the exhaust passes through tubes (exhaust pipes) to the catalytic converter and ultimately to the muffler and out of the tailpipe at the rear of the vehicle.
Inside the muffler are several sound-deadening chambers and sound-absorbing materials that are used to dampen the noise produced by exhaust gasses.
Since the main purpose of a muffler is to dampen engine noise, the most common sign that a vehicle might need a new muffler is a louder sound when the engine is running. A change in the volume of the sound of your engine can happen gradually or all at once, depending on the problem with your muffler.
Other symptoms can also point to a bad muffler. A rattling noise coming from underneath the vehicle can indicate a corroded or broken muffler mount or tailpipe. The smell of exhaust fumes inside your vehicle can reveal an exhaust leak. Even a drop in fuel economy or an engine misfire can sometimes be attributed to a bad muffler if the exhaust flows either too freely or too restrictively through the muffler.
To replace a muffler, a technician will first need to lift and support your vehicle in the air for access. From there, the process to remove and replace a muffler depends on whether the component is bolted or welded in place. If bolted, it is common for the fasteners to be corroded and difficult to remove. If welded, the old muffler must be cut away from the exhaust pipe, and the new muffler welded on.
Most mufflers are held in place with rubber mounts. These mounts need to be removed so that the exhaust system can hang down enough to gain clearance. Once the exhaust system has been lowered sufficiently, the exhaust pipe ahead of the muffler is either unbolted or measured and cut. Then the muffler is extracted, and the tailpipe is cut off before the new muffler is set in place and bolted or welded.
Some mufflers come with additional hardware, such as bolt-on flanges, tailpipes, and exhaust gaskets. Others require that the entire exhaust system be removed from the vehicle in order to install a new muffler.