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Old 02-17-2003, 12:45 PM
RunningTooHot's Avatar
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Question Cabin noise reduction & new muffler???

Maybe Im just being more sensitive to the noise lately or maybe mufflers wear out internally?

I am wondering if anyone has had a noticeable drop in interior cabin noise at freeway speeds when they have replaced the center resonator and the rear muffler? If so, could you please say how much of a difference there was, and what was the condition of the exhaust system that you replaced?

My cars exhaust system is original (1984 300D, 220,000 miles) and there are not any large holes or anything, but it looks like corrosion is just starting to surface. I am wondering if the internal baffles start to rot out & cause a progressive increase in noise, especially when the engine is under load. There is a LARGE difference in noise levels when traveling 70mph and coasting versus cruising. The noise is not just the injection pump and injectors it is a pretty significant roaring.

Any input would be greatly appreciated.
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Old 02-17-2003, 02:04 PM
lrg lrg is offline
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Join Date: Jul 2001
Location: San Francisco
Posts: 1,163
The center resonator on my W123 rusted on the top so it was leaking and slightly louder. It took me a while to realize it because I couldn't see any rust but eventually I started getting fumes drawn into the passenger compartment so it was obvious I had a hole somewhere. Take a look the next time you are under your car to see if there is any soot buildup around the mufflers. If so you may have a leak on top that you can't see. My new exhaust did make my car a bit quieter but not by a whole lot.
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold
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Old 02-17-2003, 02:14 PM
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Join Date: Jul 2002
Posts: 1,141

Noise on W123's is been a hot issue for a long time. First, these cars WERE not loud new. Only anoiance at highway speeds suggest deterioration in weatherstripping, firewall seals, and engine insulation.

My car, there was a very small tear in the floor board and it made the drivers side hugely noisy- drop of sealant and it's quiter. Every hole in the firewall has a seal. AC lines, gas pedal, speedometer cable, wiring, oil pressure line. If you start digging around, I bet some or all of these have deteriorated. You can replace them or some people use some silicone to seal them.

You can email me directly, I've done some of this to several cars.

Michael McGuire
83 300d
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD
86 300E
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Old 02-17-2003, 05:45 PM
Join Date: Jul 2001
Location: Old Lyme, Connecticut
Posts: 3,596

On my 1982 240D my daughter started complaining about the car getting louder and I began looking it over. The exhaust system was a little used here and there so we put a new pipe in from the manifold to the resonator, and a new resonator. Helped but did not completely solve the problem. Then I found the flexible connection between the intake and exhaust controlled by the EGR valve had a big hole in it. Changed that (very sharp edges!) and it got a little better. So I left it alone for a while and she continued to complain. Then I found the exhaust manifold was loose. New gasket for intake and exhaust and new fasteners, and the problem was conquered. It is still not a quiet car, but I think it is back to its original annoying noise level instead of objectionable level. At least my daughter's response changed, so I count that as a success. Good luck, Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)
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