2004 BMW 645Ci Exhaust Muffler Replacement Cost

The muffler uses several sound deadening chambers that absorb vibrations as the exhaust gas passes through this forced maze. After passing through multiple chambers and baffles, the exhaust noise is quieted down to the designed level.

When the muffler has become sufficiently corroded it will no longer muffle the exhaust noise properly. The muffler brackets or rubber hangers can also break, allowing it to swing underneath the vehicle and hit the undercarriage. Some high end vehicles have vacuum or electronically actuated flaps that adjust the noise level, and when faulty can cause rattling noises from the tailpipe, or excess noise when the flaps are stuck open. In the rare case the muffler is clogged, they engine may fail to start, stall, or run roughly due to excess back-pressure.

Driving a vehicle with a hole in the muffler will generally not cause any harm. The engine will not record any data concerning the muffler, because the oxygen sensor is located before the resonator and muffler. If the muffler is clogged, the vehicle will most likely not be able to start, or stay running.

The number one cause of muffler failure is corrosion from road salt or other debris. Collisions can also damage mufflers when the vehicle is rear ended. There is no recommended replacement interval for mufflers, and they often last the life of the vehicle.

Diagnosis of a muffler issue is typically visual in nature. The condition of the muffler, exhaust pipe, and hangars will be inspected, and any corrosion or excessive wear will necessitate replacement. Furthermore, if the engine will not start, and no air comes from the exhaust pipe, the muffler may be disconnected to locate the clog. If the muffler is clogged, it will be replaced.

Replacement varies with vehicle type. Many factory mufflers only require the rear most section to be unbolted and replaced with new. Because of the location, usage of penetrating chemicals and heat may be required to free the corrosion on the fasteners. If installing an aftermarket muffler with different flanges, cutting and welding of the original exhaust pipe may be necessary to fit the new one.

While the muffler is off for replacement, consider replacing the rubber hangers or "donuts". If these are worn or missing, the muffler will move around unrestricted and cause the junctions to fail even on quality replacements.

With exception to some high-end aftermarket performance systems, the OEM muffler is usually the best one for your vehicle. Having a shop weld on an off the shelf muffler will be cheaper in the short run, but may fail more often depending on the quality of the aftermarket muffler, and the quality of the shop's welding ability.

Replacing a muffler is only a DIY capable project if the existing muffler and replacement muffler can be changed without welding. If welding is required, a professional exhaust welder should complete the repair.