The Ins and Outs of Your Car's Intestines

A car's exhaust system works like human intestines- both remove waste in order for the body (yours or your car's) to stay healthy.

The automobile engine's combustion produces hot exhaust gases such as hydrocarbons, nitrogen oxides, carbon monoxide, sulfur dioxide, phosphorus, and the occasional molecule of a heavy metal such as lead or molybdenum. They are not only poisonous, but create pollution and contribute to the disappearing protective ozone layer around the earth. This push of waste from the engine also creates loud noises. I'm sure many of you have experienced a muffler falling off and the need to shout at the person sitting beside you because your sweet little car sounds like a motor head's dream machine.

Please notice I said exhaust system. It takes a series of small parts and pieces welded together to achieve this monumental task of cleaning up your car's waste and keeping it quiet.

First in line is the Exhaust Manifold. Attached to the engine, this set of cast iron pipes funnel all the exhaust ports into one pipe so you don't have four exhaust pipes sticking out the back of your car. The gases gather here and are pushed by the continuing pressure of incoming gases into the Headpipe, which connects the manifold to the very important Catalytic Converter.

The "cat's" main job is cleaning up some of the harmful chemicals from the waste gases, so you don't end up breathing them or having them enter the atmosphere. It is filled with ceramic honeycomb or ceramic beads that are coated in platinum and palladium. When the gases run into this treated ceramic, it causes a chemical reaction turning them into carbon dioxide, nitrogen, oxygen, and water vapor.

These changed gases next go into the Muffler. This oblong metal device catches the noise the internal combustion creates by routing the sound waves through a series of chambers, baffle plates, or other mechanical designs that bounce sound waves off of each other and, eventually, cancel each other out, getting rid of the vroom, vroom the car would make without it. Some cars also have a Resonator. This is another sound-reducing device and can be found before or after the muffler.

The Tailpipe is the last stretch of piping that connects to the muffler (or resonator) and stops at the side or back of your vehicle. These pipes usually have bends to curve up and over the rear axle.

There are also sensors important to the exhaust system, which monitor air/fuel mixture. If the mixture is out of balance, there is increased fuel consumption as well as emissions leaking into your exhaust, which can make your Check Engine light come on. The sensors tend to wear out faster than their metal counterparts. Plus Vermont's excess road splash, salt, oil, and dirt speed up the aging process. If the sensor fails, it can cause surging or hesitating while driving or damage the catalytic converter, which is and expensive part to replace.

Unlike the sensors, the metals used today to make exhaust parts last longer than they used to: typically it's about five to seven years before any big pieces need to be replaced.

The exceptions to this rule are automobiles that only go on short trips, especially during the winter. Since the muffler and pipes never get hot enough to evaporate any collected water, this type of driving can cause the muffler to rust from the inside out.

Also, mufflers that are mounted far from the catalytic converter or mounted behind the rear axle are at risk of having moisture puddle inside. The water combining with sulfur in the exhaust forms a highly corrosive acid that eats away at the metal.

What often happens is the gaskets or flanges connecting parts deteriorate and exhaust gases leak out. You want to have the gasket or flange replaced ASAP for two reasons. First, the gases are colorless and odorless- and can be lethal. Even a small leak of exhaust gases getting into your car can affect your judgment and perception. That headache you thought was caused by the long drive home may be poisonous gases trickling into the passenger compartment. Second, changing the gasket or replacing the flange is relatively cheap compared to having two pieces break apart while you are driving and the resulting damage not only to the exhaust but a tire, axle, or other part.

With potholes abounding on the roads, ask your mechanic to do you a big favor by inspecting your car's exhaust system when it next goes into the shop for service or repair. You want them to tighten those annoying heat shields that continually get loose and rattle, and keep an eye our for any small exhaust leaks before they become a bigger, more expensive problem down the road.

Happy Motoring,

Amy