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  #1  
Old 10-16-2006, 06:41 PM
OMEGAMAN's Avatar
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Cabin noise 1982 300D TURBO

My benz makes lots of noise on the interstate. When I get it up to 75 it roars. I was thinking of replacing the rear muffler but it has no rust holes or dents.
Does anyone know if there is maybe fiberglass in these mufflers for sound damping? If so I'm sure it would be all gone after 300,000 miles and causing my loud engine sound at high speeds.
Any thoughts on this. Anyone replaced their muffler for this reason?


Last edited by OMEGAMAN; 10-16-2006 at 07:05 PM.
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  #2  
Old 10-16-2006, 08:17 PM
Tom Scordato
 
Join Date: Feb 2005
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Cabin Noise

Omegaman, They are loud to some. I have owned a 1977 300D and now a 1979 240D, both non turbos and they are quite a bit louder than a gasser. There was a guy some years back who made a shroud of some sort to go around the engine, but I think he is out of business.

I have used these cars so long as my daily highway driver that I do not notice it anymore.

Regards Tom
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  #3  
Old 10-16-2006, 08:18 PM
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yea, i noticed a nice roar at 90 mph.. and a nice cloud of soot when i let off the go pedal.. ^_^
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  #4  
Old 10-16-2006, 08:44 PM
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These mufflers are your typical internally-baffled design with no fiberglass. They tend to rot from the inside out, so while the muffler case may be in good shape, it could be rotted out on the inside.

However, even if the muffler is brand new a W123 diesel will make alot of noise. Soundproofing like Dynamat on the interior firewall would help if you feel like removing the dash. I think most people just learn do deal with the noise. If you end up replacing the muffler, be sure to avoid aftermarket "discount" junk like you find at Meineke or Midas. OEM may cost more, but it's cheaper in the long run.
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  #5  
Old 10-17-2006, 01:37 AM
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I wont get a cheap aftermarket muffler. The oem muffler is only $100 on this site so I think I'll do that. Hope I dont need a resonator too thats another $100.
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  #6  
Old 10-17-2006, 08:29 AM
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Sure you could have a muffler with the baffles rotted out. More likely though is the general homoginization of all the operating noises like one 240d of mine. One ebay member mentioned that these cars need alll engine motor mount components in tip top shape, good quality hoodpad etc to keep the noise to reasonable levels. One of my 240s for example is almost twice as loud at 70 mph as the other but I do not think it is exhaust noise. Yes, I know but both can really cruise at 70 with a tailwind going downhill. My 123 naturally aspired 300d is a little loud and noisy at cruise as well. I blame that partially on the rear axel ratio. Just being the exhaust noise component for you would be a nice way out and of course it is possible. That guy that made a shell to enclose his engine as mentioned was not totally out to lunch in my opinion. I also believe you are a working mechanic and that increases your chances of being right. Let us know if there is any improvement as noise supression is a worthwhile effort on some of these cars. Common sense is that they could not have sold them new originally if they were as noisey as some examples of ours now are at speed.

Last edited by barry123400; 10-17-2006 at 08:41 AM.
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  #7  
Old 10-17-2006, 09:44 AM
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Quote:
Originally Posted by barry123400 View Post
Sure you could have a muffler with the baffles rotted out. More likely though is the general homoginization of all the operating noises like one 240d of mine. One ebay member mentioned that these cars need alll engine motor mount components in tip top shape, good quality hoodpad etc to keep the noise to reasonable levels. One of my 240s for example is almost twice as loud at 70 mph as the other but I do not think it is exhaust noise. Yes, I know but both can really cruise at 70 with a tailwind going downhill. My 123 naturally aspired 300d is a little loud and noisy at cruise as well. I blame that partially on the rear axel ratio. Just being the exhaust noise component for you would be a nice way out and of course it is possible. That guy that made a shell to enclose his engine as mentioned was not totally out to lunch in my opinion. I also believe you are a working mechanic and that increases your chances of being right. Let us know if there is any improvement as noise supression is a worthwhile effort on some of these cars. Common sense is that they could not have sold them new originally if they were as noisey as some examples of ours now are at speed.
Exactly not many people would have bought these if they were this noisy from the factory.
One of my customers has the same car as I do with half the miles. It has a new muffler on it and is very quiet compared to mine. I wonder what a difference motor mounts would make. Mine arent torn but they are mushy.
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  #8  
Old 10-17-2006, 07:12 PM
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I think it was Tom the architect fellow on site that tried to bring some of us up to speed regarding the cause of noise levels in 123 diesels. Over time I think what he proposed to others makes sense. You also make sense including the possibility of the resonator as well. Especially if it is original. When I inspected exhaust systems in central alabama it was obvious that oxidation inside could be really bad with the outside looking about as new. We have so much salt here that internal failures are pretty rare as the oxidation from the outside is so fast that failure of internals is not likely. Ome is the longest lived by far but only about five years from new you will be replacing the majority of it here. Perhaps a little longer on the more recent cars.
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  #9  
Old 10-17-2006, 08:41 PM
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Bad mounts

Quote:
Originally Posted by OMEGAMAN View Post
Exactly not many people would have bought these if they were this noisy from the factory.
One of my customers has the same car as I do with half the miles. It has a new muffler on it and is very quiet compared to mine. I wonder what a difference motor mounts would make. Mine aren't torn but they are mushy.
Hood Pad
http://www.peachparts.com/shopforum/diesel-discussion/141824-hood-pad-diy-links.html#post1061578

Bad engine mounts
http://www.peachparts.com/shopforum/diesel-discussion/121286-bad-engine-mounts-post868339.html

Heat shield OM617 engine mount
http://www.peachparts.com/shopforum/diesel-discussion/121452-heat-shield-om617-engine-mount-post873875.html

Engine / motor mount DIY
http://www.peachparts.com/shopforum/diesel-discussion/146482-engine-motor-mount-diy.html#post1104023

Vibration Cured
http://www.peachparts.com/shopforum/diesel-discussion/123307-vibration-cured.html#post885163



Bad Flex Disc
http://www.peachparts.com/shopforum/diesel-discussion/121285-bad-flex-disc-post868329.html
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  #10  
Old 10-17-2006, 09:59 PM
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Good links Mr. Hunter.

My 82 240D developed a roaring sound @245K without any perceivable vibration...after checking the Mounts, Flex disc, Carrier bearing, muffler, and ruling them out it turned out to be the right half-axle needing repair. The roaring sounded somewhat like a doppler effect with sort of a low pulsing rumble. I think Stretch helped to diagnose the problem.

Anyway, traded a couple of cases of Coors to a buddy to do the mechanics, replaced the half-axle with a good low mileage $75 replacement from the junkyard and the noise vanished.

That was at least 20 years ago so the beer was probably near market price for the labor back then...
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  #11  
Old 10-17-2006, 11:34 PM
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I had a big chunk of 1" foam rubber left over from a project and the red-head was in a throw everything out of the nest mode. Instead of chunking the foam in the trash, I pulled the floor matts and cut the foam to size and installed it under the floor matts.

It does help the road noise and it is very cushy under foot.

However, I lean towards a new muffler. Mine still "looks" great...but after 23 years of use, you gotta wonder what is still left inside!
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  #12  
Old 10-18-2006, 02:04 AM
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Disagree

I have driven my 1985 300SD with no exhaust (broken down pipe) for days.
The noise difference is only on power take off from a stop.
On the expressway it was just as quiet with as without an exhaust.

I have driven too many 240D, 300D and 300SD with bad mounts, axle shafts, differentials, bearings, flex disc, steering, suspension, sunroof and door seals.

I hear thousands of sounds, which one is the issue?
Noise complaints are tough, even when the customer is in the car with you.

An audio file of your car noise may help...

Last edited by whunter; 10-18-2006 at 05:58 PM.
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  #13  
Old 10-18-2006, 10:36 AM
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Custom fitting an old carpet and lining the trunk w/ it will help deaden the noise. Did that on an old Rabbit and it didn't cost me a penny.
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  #14  
Old 10-18-2006, 11:09 AM
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Quote:
Originally Posted by NoSpark View Post
Custom fitting an old carpet and lining the trunk w/ it will help deaden the noise. Did that on an old Rabbit and it didn't cost me a penny.
I do notice if the trunk is full of stuff the car is a lot quieter on the interstate. I may try that. I have a rear window seal on order right now so when that gets replaced that may be the next thing.
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  #15  
Old 10-18-2006, 11:23 AM
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Great advice from whunter, as always. He answered my very first question on this forum.

My original muffler has one pinhole on the bottom and a couple of small dents. I know that the baffles are a little rotted because I hear some rattling when I shake the muffler (baffle debris- sounds like a pinch of sand in the muffler). I still don't get what I would consider excessive tailpipe noise, though. I'll probably replace the exhaust within the next few years, when it gets bad enough to warrant replacing it. At the rate it is going bad I may get another five years from my exhaust.

New door seals did a great job of reducing wind noise, but it still sounds like there's a lion in a blender on the other side of my firewall. I still need to do the window sweepers (correct nomenclature?). My hood pad is about 50% gone, and it's on my to-do list. My motor mounts are good, engine runs as smoothly as it should, new air cleaner mount bushings, etc.. I'm thinking that the only way to really quiet it down at highway speeds is improved cabin insulation, particularly on the firewall. I'm waiting for my evaporator to need replacement, as that's the only thing that'll make me pull the dash. When that happens, I'll cocoon the firewall in dynamat . I've also been pondering door insulation options.

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