1999 Audi A8 Exhaust Pipe Replacement Cost

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.

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.

A vehicle can be driven without a portion of the exhaust system, however, this is not recommended. Aside from pollution and legalities of having a properly functioning exhaust system, a leaking exhaust pipe is likely robbing you of fuel mileage, and the hot discharge from the exhaust leak may be overheating one of many components on the undercarriage. Having the exhaust system repaired at the soonest opportunity is the best course of action to return your vehicle to proper operating conditions.

Exhaust systems incur enough failures that specialized shops for exhaust systems have sprung up in most towns around the country. However, the typical repair is more likely to be a muffler, catalytic converter, oxygen sensor, or exhaust manifold gasket. Exhaust pipes are made corrosion resistant, and it takes many years for that material to break down under dry conditions. This is why most vehicles in dry climates will never need a section of the exhaust pipe replaced. Those who live in areas frequented by snow, road salts, heavy rains, and high humidity are at higher risk of needing the exhaust pipe replaced, and this can become a necessity in only a few years in the northeast united states.

Diagnosing a leaking or perforated exhaust pipe simply involves looking for the leak, or following the sound. Exhaust pulses from a leaky exhaust pipe are unmistakeable to the trained ear, and are sure to be the loudest thing under the vehicle. Listening for a leak, and focusing on the rusted or corroded portions of the exhaust pipe will soon yield the discovery of the leak.

Since exhaust pipes are either clamped together or welded on, the replacement procedure may be to cut off the portion of the pipe needed replacement, or disconnect the portion of pipe at the clamping location. Once the bad section of exhaust pipe is removed, the new section can be cut to size, fitted, and clamped or welded in place. If the portion of the exhaust has been ordered from the manufacturer, only removing and replacing the fasteners is typical, but if the pipe is being repaired from raw pipe, the technician will likely need to bend the pipe to match the old section before refitting and welding or fastening the pipe in place.

If one portion of the exhaust pipe is perforated due to corrosion, it is likely that another location will soon have the same issue. having the entire exhaust system inspected for corrosion and damage can prevent a return trip to the shop in the near future. Also, the rubber and metal brackets used to secure the exhaust to the vehicle should be inspected, as the exhaust system is fairly heavy and will encourage corrosion to create perforations if not secured properly.

While repairing the exhaust pipe, it is extremely important not to bump or misshape the heat shields surrounding the exhaust system. Changing the position of the heat shields will nearly always cause the heat shields to vibrate at certain engine speeds due to engine vibration frequencies at those speeds. There are many sizes of exhaust pipe, and ensuring that the inside diameter of the exhaust pipe matches the replacement section will help avoid issues during installation. Always measure the pipe before purchasing a replacement section.

For bolt-on replacements, changing a section of the pipe is simple, especially if there is no oxygen sensor to change. That being said, if the pipe is to be manufactured for the vehicle, attaching flanges and installing the pipe will require pipe bending equipment and welding equipment. If this is the case, most DIYers will not have the tools or training to accomplish this task. On bolt-on applications, the exhaust bolts will likely be rusted, seized, and fragile, and heat or cutting may be required to remove the fasteners from the vehicle. If there is any doubt about removing the bolts, it may be best left to a professional.