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Muffler/Tailpipe Replacement
 
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Pelican Technical Article:

Muffler/Tailpipe Replacement

Tom Morr

Time:

2 hours2 hrs

Tab:

$585 to $1,144

Talent:

**

Tools:

Floor jack or ramps, screwdriver, ratchet, sockets, combination wrenches, T50 Torx bit

Applicable Models:

Mercedes-Benz R170 (1998-04)

Parts Required:

Replacement muffler/tailpipe assembly

Hot Tip:

Apply penetrating lubricant to the flanges' hardware, or cut off corroded hardware.

Performance Gain:

A freer-flowing muffler can increase engine power and sound quality.

Complementary Modification:

Replace the rubber hangers and catalytic converter (if the car fails emissions testing or the car has a rocks-in-coffee-can rattle).

Sparks often fly at muffler shops, so M-B owners might assume that welding and cutting automatically come with the territory when doing exhaust work. This isn't necessarily the case.

Granted, patching new mufflers into existing pipes usually requires metalwork. Some enthusiasts have the rudimentary welding and cutting tools and skills. But installing a direct-replacement "after-cat" system: the components downstream from the catalytic converter: is often a bolt-on job. (The M-B replacement part number for our project 2000 SLK 230 Kompressor is 170-490-02-21.) Having a second set of hands is handy, but the job can be done by a lone home mechanic in a couple hours (fasteners willing).

Some R170 SLK owners prefer a non-M-B exhaust sound. Luckily, the web has several video clips of various kits' sound qualities. Other owners simply want to replace a rotted existing system with factory-replacement parts. Regardless of the motives, the steps are the same: assuming that the new kit mimics the OEM routing and mounting locations.

Rattles often come from loose hangers or heat shields. These sometimes reveal themselves by hand-jiggling and tapping the exhaust when it's cool. Harder-to-find exhaust rattles can be located by raising and securing the vehicle. Of course, jack up your car in a safe fashion. We have an article on the site that adroitly addresses this very issue. Have a helper accelerate the engine while listening to the exhaust from underneath, using a two-foot-long piece of one- to two-inch OD non-ferrous pipe (less heat absorption) as a stethoscope. Move along the exhaust at approximately four-inch increments until the sound source is localized.

After-cat systems often include gaskets and mounting hardware. Pelican Parts sells gaskets separately.

Spray the existing hardware with penetrating lubricant. If they still won't come undone, cut the bolts between the flanges with a die-grinder, hack saw, reciprocating saw, or comparable tool.

Consider replacing the rubber hangers ("donuts"). They're one of the car's fastest-deteriorating parts. Pelican Parts sells these individually.

When bolting on the new exhaust, rotate bolts in a circular pattern, giving each a few turns at a time. This helps keep the gasket centered as the flanges come closer together.

Following the installation, check for exhaust leaks. Hold a piece of paper at various points around the gasket and check for turbulence. Be cautious when working around hot exhaust parts.

Check bolt tightness after the car reaches operating temperature a few times. We couldn't find an official torque spec, but thermal expansion and contraction can cause fasteners to loosen.

Begin by raising and securing the car to create workspace.
Figure 1

Begin by raising and securing the car to create workspace. The left rear cross-brace must be removed, requiring a T50 Torx bit or wrench. The existing fasteners sometimes come apart without a fight. Penetrating spray can help them break free.

The OEM exhaust system has a grounding flange in front of the rear axle.
Figure 2

The OEM exhaust system has a grounding flange in front of the rear axle. Unbolt the ground strap while the three main mounting bolts marinate in penetrant.

The OEM muffler also has a grounding flange (arrow).
Figure 3

The OEM muffler also has a grounding flange (arrow). The ground strap is secured with a 12mm-headed bolt. This muffler is corroding at the tailpipe and also at its lower seams.

The muffler is suspended by a rubber hanger on each side (arrow).
Figure 4

The muffler is suspended by a rubber hanger on each side (arrow). Hand space is tight between the body and bumper, but the muffler can be lifted slightly, then the hangers slid outward off the muffler's mounting horns.

Luckily, these exhaust fasteners came apart without incident.
Figure 5

Luckily, these exhaust fasteners came apart without incident. The head takes a 13mm wrench; the nut is 12mm. Heavily corroded bolts can be cut between the flanges, then replaced.

The replacement exhaust kit likely includes a gasket (arrow).
Figure 6

The replacement exhaust kit likely includes a gasket (arrow). If not, be sure to replace the gasket: cheap insurance against an annoying exhaust leak.

Once the pipe and muffler are unfastened, the rear exhaust
Figure 7

Once the pipe and muffler are unfastened, the rear exhaust "after-cat" assembly can be slid forward off the center hanger (arrow) and removed from the car.

We used the existing exhaust system for demonstration purposes.
Figure 8

We used the existing exhaust system for demonstration purposes. Aftermarket systems are often DIY bolt-in direct replacements, assuming they have the hangers (arrows) in the factory locations and a mounting flange. Pelican Parts sells OE and aftermarket systems, in addition to rubber hangers and gaskets.

The muffler's rubber
Figure 9

The muffler's rubber "donut" hangers suspend it from the car. Access is tight with the muffler in place. Shops often put the hangers on the muffler, then use a curved pick tool to slide them over the body bracket. We installed the hangers on the car first: the muffler horns are slightly more reachable once the exhaust is bolted in place.

Reverse the disassembly steps to install the exhaust system.
Figure 10

Reverse the disassembly steps to install the exhaust system. We were able to pull one rubber hanger down over the muffler mount. We then used a flat-blade screwdriver to slide the second hanger into place.

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Comments and Suggestions:
Daniel Comments: Where exactly is the muffler bumper located?
September 12, 2016
  Followup from the Pelican Staff: I am not sure what you are asking. - Nick at Pelican Parts  
Boggie Comments: Hi
Msny thanks for your advice. I did what you suggested and removed the quaterlight assembly using your technical guide. I found that the upper cable guide had partially come out of its mounting point due to the centre pub being loose. This caused the cable to come off its guide causing the loud clunk I heard. I replaced the centre pin with a slightly larger one and re- fixed the guide, then the cable. Apart from my time which was around 3 hours this was a zero cost repair saving me at least $too in main dealer charges. GREAT RESULT!Many thanks to Pelican Parts
June 2, 2016
  Followup from the Pelican Staff: Thanks for the follow up. We appreciate it.
- Nick at Pelican Parts
 
Boggie Comments: Hi, I just discovered your site and I have to say I am very impressed.
I had the roof down on my R170 SLK today, but when I put it up again there was a loud CLUNK from the left quarter light area. The roof went up ok, but the left quaterlight and the font left window stayed down. What could have happened?
Any ideas greatly appreciated. I have looked at your quaterlight removal article and am capable of the work, being also an XKE owner.
May 24, 2016
  Followup from the Pelican Staff: Sounds like the regulator may have failed. It's worth starting there. - Nick at Pelican Parts  

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