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Pelican Technical Article:

Exhaust System Replacement

Nick Czerula

Time:

2 hours2 hrs

Tab:

$500

Talent:

***

Tools:

Set of sockets (10mm, 13mm, T45 Torx) pipe cutter, pry bar, floor jack, jack stands, wheel chocks, safety glasses, torque wrench

Applicable Models:

Mercedes-Benz W211 (2003-09)

Parts Required:

Exhaust system, exhaust gaskets, exhaust fasteners, rubber exhaust insulators

Hot Tip:

Work with a cool exhaust

Performance Gain:

Replace worn exhaust system

Complementary Modification:

Use performance exhaust

The exhaust system wears out and becomes leaky with age. A leaky exhaust can be a severe health hazard to passengers, if odorless CO or other exhaust gases find their way into the cabin. A leaky exhaust system is usually far noisier than an intact one. Finally, bear in mind that the catalytic converters and oxygen sensors, an integral part of any modern automobile exhaust system, are critical to the emissions control system of the vehicle. Generally speaking, a vehicle with defective exhaust system fails most annual state safety and emissions tests, because of the safety hazard, excess noise and emission control failure.

When replacing your exhaust system remove the entire unit as one piece. Once the exhaust has been removed, repairs or modifications can be made. Keep in mind that a number of other repairs, such as the driveshaft replacement, transmission removal and fuel tank removal require that the exhaust system be completely removed from the vehicle.

You can replace the rear muffler with the exhaust installed. When removing the exhaust system, have new fasteners, gaskets and rubber insulators on hand. These parts wear out just like the exhaust system. Having new ones on hand helps to complete the repair. To replace individual front exhaust pipes, you can split the exhaust at the center muffler, then remove the side of the front exhaust that you need to.

Damaged catalytic converters or failed oxygen sensors mostly cannot be diagnosed visually. Before you remove the exhaust system, use a Mercedes-Benz scan tool or equivalent to download fault codes and determine if there is any reason to suspect the failure of these major emissions control components. The oxygen sensors, particularly those downstream of the catalysts, may be easier to remove once the exhaust system is off the car.

When removing the exhaust system and particularly if you are going to store it while other repairs are taking place, be sure to protect the oxygen sensors and their electrical leads. Do not drag the exhaust system on the ground carelessly.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability.

Vehicle models change and evolve as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Raise and support the vehicle on jack stands. If you raise just the rear, you should have enough space to work at the front of the exhaust. If not, raise the front of the vehicle to work on the front, then raise the rear of the vehicle when removing the exhaust system. See our tech article on jacking up your vehicle. Be sure to always wear safety glasses whenever you work under your car.

With the vehicle raised you have a clear view of the exhaust system.
Figure 1

With the vehicle raised you have a clear view of the exhaust system. You can replace the left rear muffler with the exhaust installed by separating it at the clamping point (red arrows). The right side muffler is replaced along with the center muffler (yellow arrows). The front exhaust pipe with integrated catalytic converters can be replaced (green arrows) independently.

Support the exhaust system from below using a hydraulic floor jack or jack stand (green arrows).
Figure 2

Support the exhaust system from below using a hydraulic floor jack or jack stand (green arrows). I like to put the jack under each rear muffler or the center muffler, depending on what I am replacing.

Next, you have to detach the rear exhaust supports.
Figure 3

Next, you have to detach the rear exhaust supports. You will need to detach these whether you are replacing the mufflers, or the entire exhaust. If replacing the front pipes and catalytic converters, this step can be skipped. Working at the four rear exhaust hangers (red arrows), use a pry bar (yellow arrow) to lever the rubber insulator (green arrow) off the support. Use soapy water to lubricate the insulators if necessary.

If replacing the left side muffler, loosen the 13mm exhaust clamp (red arrows) and slide the clamp off the pipe union.
Figure 4

If replacing the left side muffler, loosen the 13mm exhaust clamp (red arrows) and slide the clamp off the pipe union. Then remove the 13mm fastener from the exhaust support (green arrow). If you're removing the entire exhaust, leave these items connected.

If you're replacing the right side and center mufflers, remove the four 13mm flange fasteners (green arrows).
Figure 5

If you're replacing the right side and center mufflers, remove the four 13mm flange fasteners (green arrows). Note the crack in the flange (red arrow). If you find a cracked flange on a component you are reinstalling once removed, you can repair it using a split flange. If removing the entire exhaust, leave these items connected.

Continuing with the removal procedure for the entire exhaust system, you will have to remove the support that connects the exhaust tunnel (green arrow).
Figure 6

Continuing with the removal procedure for the entire exhaust system, you will have to remove the support that connects the exhaust tunnel (green arrow). Working at the center of the vehicle, just behind the catalytic converters, remove the T45 Torx (yellow arrows) support (red arrow) fasteners. Hold the support so it doesn't fall as you remove the final fastener.

Remove the support.
Figure 7

Remove the support.

Locate and mark the oxygen sensor electrical connectors: Bank 1 Sensor 1, red arrow; Bank 2 Sensor 1, green arrow; Bank 1 Sensor 2, blue arrow; Bank 2 Sensor 2, yellow arrow.
Figure 8

Locate and mark the oxygen sensor electrical connectors: Bank 1 Sensor 1, red arrow; Bank 2 Sensor 1, green arrow; Bank 1 Sensor 2, blue arrow; Bank 2 Sensor 2, yellow arrow.

Label or mark the wiring harness to aide during reinstallation.
Figure 9

Label or mark the wiring harness to aide during reinstallation. Pull the wiring harness out of the mount. Then disconnect the electrical connector by pulling it straight apart (inset).

Once the oxygen sensors are disconnected, move to the right side of the transmission bell housing.
Figure 10

Once the oxygen sensors are disconnected, move to the right side of the transmission bell housing. Detach the oxygen sensor wiring harness (red arrow) from the mount (green arrow) and pull it out of the clips. Follow the left side harness up around the exhaust. Cut or remove any zip ties securing the harness to the engine.

Now it is time to remove the exhaust connection at the manifolds.
Figure 11

Now it is time to remove the exhaust connection at the manifolds. Start on the right side of the engine and remove the two 13mm front pipe fasteners (red arrows). Be careful when loosening these fasteners. I like to spray them with penetrating oil before removing. Depending on your region, these can seize up. If they break, don't worry. You can remove the broken bolts and capture nuts by hammering them out.

Move to the left side of the engine, remove the same 13mm fasteners you did on the right side.
Figure 12

Move to the left side of the engine, remove the same 13mm fasteners you did on the right side. Access is tougher on the left side. For the rear fastener, I access it from the left side next to the pipe (green arrow). For the front fastener, I access it from in front (red arrow) near the front axle (yellow arrow), if equipped with 4MATIC. RWD I access the same way, minus the obstruction from the axle.

Next, working at the center of the vehicle, the center support has to be removed.
Figure 13

Next, working at the center of the vehicle, the center support has to be removed. Start by loosening the four 12mm nuts (red arrows). Then remove the two 13mm fasteners (green arrows). Then remove the insulator plate from the vehicle (yellow arrow).

Pull the exhaust back away from the exhaust manifolds and lower it.
Figure 14

Pull the exhaust back away from the exhaust manifolds and lower it. Then remove the exhaust from the vehicle. It is helpful to have a friend assist with this part of the task, as the exhaust can be hard to manage. Once the exhaust has been removed, you can replace the front mufflers or repair the system as needed. Line up the new parts with the old ones. Mark where you will cut. Use a pipe cutter to cut the pipes. Then remove any sharp edges from the pipes. Install the new parts using the exhaust clamps. Then reinstall the exhaust system. Be sure to replace any hangers, fasteners or flanges if they are in bad shape.

If you broke a fastener during removal, cut the fastener (red arrow) so about one-inch hangs out of the manifold.
Figure 15

If you broke a fastener during removal, cut the fastener (red arrow) so about one-inch hangs out of the manifold. Then tap the broken fastener up to remove it along with the captured nut. Once out, install the new captured nut (green arrow).

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Page last updated: Mon 12/5/2016 02:45:53 AM