What is an Exhaust Pipe?
As the engine burns fuel to mechanical power, the liquid fuel is turned into a gaseous state full of toxic chemicals. Instead of letting these exhaust gases vent into the air we breath, an exhaust system is used to channel these gases through a cleaning process, quiet the noise of combustion, and vent the filtered air from the back of the vehicle. To direct these gases through converters and mufflers, metal exhaust pipes are used. These metal pipes can withstand the abuse of high heat, and the corrosive properties of gasoline and road debris to last for many years.

How does an Exhaust Pipe work?
The exhaust pipe works like any other pipe, as it channels exhaust gas from one place to the next. It begins at the exhaust manifold flange, moves down to a specialty pipe called a 'flex pipe', and from there a new portion of the exhaust pipe extends from the flex pipe to the catalytic converter. This section of the pipe will contain an oxygen sensor, allowing the computer to analyze the exhaust before cleaning in the catalytic converter. After the catalytic converter, another section of exhaust pipe will move the cleaned exhaust to the muffler, and an oxygen sensor on that portion of the pipe will allow the computer to analyze the gases after cleaning. This provides a measurement of the efficiency of the catalytic convertor(s). Finally, the muffler is attached, and quiets down the noise from the engine. Attached to the muffler is the tail pipe, which channels the gas downwards, keeping heat away from the rear of the vehicle. This is a typical system, and there are many configurations of these parts.
What are the symptoms of a bad Exhaust Pipe?
When a portion of the exhaust pipe fails you may notice a check engine light, depending on which section has become perforated, but you will certainly notice the engine has become substantially louder and may lack power or use excessive amounts of fuel. That is because the engine may be compensating for the false readings from the oxygen sensors. Visible clues include rust or damage to the exhaust pipe, signifying an area that may be leaking exhaust and preventing the processing of exhaust gases.