I've been looking through various posts concerning noise damping on the 123 diesels. I've seen alot of testimony about how nice the MB hood pad is. Does anyone know what its made of? Does MB (or its aftermarket copycats) post any data as to acoustic loss factor or actual decibel reduction?

I've seen the posts about quilted fiberglass, though information concerning its effectiveness is purely anecdotal (not that stories are bad, just hard to compare). Anybody else out there with an oscilloscope and a microphone?

And I was just curious if anyone has tried acoustical foam - and what your results have been. I'm an engineering student at Boise State, and I've seen some pretty impressive acoustics projects demonstrating the effectiveness of a little foam. In one project, a student (Way to go Todd!) was working with Electrolux, in an attempt to make vacuum cleaners less annoying. Less than a dollar of foam (correctly placed) cut the noise levels in half.

If anyone has any ideas or information that would add to whats been posted in the past concerning acoustic damping (anecdotal or otherwise) - thats what I'm hoping for.

The MB hood pad is not only for noise reduction, but is also for keeping heat in the engine bay during winter and out (Think sun radiation) during summer.

I can understand that some people want their W12x to be a quiet as possible but the diesel klatter, even in new modern engines, is a fact of life. Personaly, I can't stand a quiet engine. I've been in a few W123's, W126's and a W116. All were way too quiet for me.

Just listen to your engine on the road, it can speak books to you that could never be heard in your driveway.

Alot can be said from a few weeks of running with only a straight pipe after your turbo.

Here is one..
http://www.peachparts.com/shopforum/showthread.php?threadid=34727&highlight=noise+reduction

An indoor appliance will not be subject to car washes... LOL.. hopefully.... so any foam would need to take that into account...

I'm one of the sickies here that doesn't think that clatter is noise, rather it's music.

For those who DO want to quieten it, the hood pad helps a little, but lead foil sandwiched between foam and lining the front floorboard and fire wall will do more than anything.

I used some of this stuff in a street rod that I built in the very early eighties and it was amazing. You have to place it smartly because obviously it is heavy, you don't want too much of it.

Good luck,

If I'm not mistaken, I think they line cabins of passenger aircraft with that stuff also.

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95 E320 Cabriolet, 169K

I am not sure if it is the same stuff... but Nova did a program which aired lately...

http://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=flight+111+fire+insulation&btnG=Google+Search

They call the one in that program " mylar"... and I don't know if that is the covering on the one TCane used....
but I think that somewhere in TCane's posts he is very specific about the fire ratings of the one he used to make his...

Hi.

Since I had alot of rust in the regular places
I had a good look at what MB did to lessen
the noise in the cabin.

The underside of the chassis is coated in a 1/4"
thick rubber under coating,which surely cuts sound.
When removing the floor mats you'll notice that
there is some sort of pad covering the metal
floor.
This,in its own right is sound proofing,unfortunately
it doesn't extend to the top of the dash,thus not
covering the whole fire wall.

If you have a leak you have to remove this stuff
because 9 out of 10 you have rust/rot under it.
I know I did.
Since you removed it and fixed the rust or you didn't
find any rust (lucky you),you'll need to replace it.
You could get a new pad from MB or you could use
the stuff that sound competitors use(dynamat or the
like,not cheap ),going this route will let you add the
sound insulation higher on the fire wall.

They also sell dynamat hood pads.
You could go as far as to add this stuff to the
firewall in the engine bay.
Cutting the noise-music-sound even more.

Just remember,if you have a turbo to add more
layers,to compensate for the extra heat.

Louis.

Thanks for the input so far guys.

I'm thinking of trying a couple of products from "dB Engineering" (http://www.800nonoise.com).

For the hood pad, their basic acoustic foam, with mylar surface treatment. Its rated continously up to 107*C and intermittently up to 135*C (whatever that means). The mylar should reflect the radiative heat back into my engine and keep it nice and toasty.

For the trunk, they have a nice foam with a vinyl covering, should be tough enough. Black vinyl should do the trick (hide the grease that its guaranteed to collect).

I think Larry is on to something with the front floorboard and firewall. I'll probly try a composite barrier called "Ultima WM2X".

This stuff is all pretty cheap compared to Dynamat, so its within my humble college budget. Any timely warnings or advice would be appreciated. I'll post my results once the stuff is installed (over a period of months).

-Zach
1981 300D (219K Miles)

I just began an install with two products from B-quiet.com
I ordered the hliner for the hood and 35 sq ft of their "Brown Bread" deadner. I put the deadner on the hood first then the hliner over it. I am lining the inside of the doors by removin the inner panels and using the peal-and-stick brown bread product. I then glued a thin layer of carpet pad (foam) on top of the deadner inside the door as well as lining the door panels with the foam before putting them back on the doors. The noise is going down with every additional layer and I believe the greatest reduction yet will be the firewall/floor.

I drove the 240 1,110 miles the day that I bought it (TX-GA) and it was a droning, draining experience. I just want to make it a more enjoyable trip when you spend hours under the wheel.

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Rick
Avid Benz watcher

Previously owned 126's: 2 1981 300SD's, 1987 300SDL, 1991 350SDL,
Previously owned 123's: 1978 300D, 1983 240D, 1985 300D
Previously owned 124: 1994 320TE

Currently:
2004 Toyota Sequoia SR5 206k
2010 Ford Edge 122k
Always looking for the next MB diesel!

I used
mineral loaded high density vinyl sheeting to sound insulate a 240D while I still had most of my hearing, with excellent results. This is the stuff used to isulate walls in buildings. It has a thin layer of foam on one side which should be placed against the vibrating surface. I put it along the floor and behind the back seat. It is easy to cut and instal. No glue is needed, the foam will hold it in placeas long as you sandwich it under the carpet. I can not recommend it for use as hood liner material. You can do an entire car for the minimum order amout ($80).

It is heavy but did not seem to effect acceleration. I can still do 0-60 in 30 seconds on a cool day in still air pointing slightly downhill. If there is any interest I will root around and fond/post the supplier info.

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JMF

I'm always curious about additional suppliers of vibration damping material. If you can, I'd really appreciate some contact info/website for your supplier.

FWIW, you can get Dynamat Xtreme "bulk packs" with something like 36 sq ft for about $125 shipped, if you hunt around enough. From what I've been told it works very well and the adhesive is excellent - doesn't detach like some other products. I still think a new MB dealer hood pad would be the best bet, maybe with a few sq ft of Dynamat on the underside of the hood before sticking the OE pad on with Liquid Nails (which I prefer over the 3M stuff because it lets you move it around before setting up, and sticks like, well, nails. )

JMF - 30 seconds? That's one quick 123!

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I had to remove the factory sound deadening from the drivers side as it simply wouldn't dry out after fixing a leak. There was trapped water 2 months after the repair despite all attemps to dry it out. I ended up replacing the factory stuff with Dynamat Original. It is much thinner but seems to work just as well. I am planning on installing a Dynamat hoodliner but haven't got around to it yet. I do like the Dynamat product and have used it before with good results. Using a heat gun on installation makes it stick very well. RT

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When all else fails, vote from the rooftops!
84' Mercedes Benz 300D Anthracite/black, 171K
03' Volkswagen Jetta TDI blue/black, 93K
93' Chevrolet C2500HD ExCab 6.5TD, Two-tone blue, 252K

FWIW, I've been told that Brown Bread is basically the same stuff as Dyna-Mat, except for costing quite a bit less.

I agree about the diesel clatter being more music than noise, but it'd be nice to be able to make things quieter for long trips. If you want ot hear the music in its full galor, you can always roll down the window

Just my $.02...I probably won't do anything with my car anytime soon; my car's quiet compared to my truck :p :p

{edited for spelling }

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2001 VW Jetta TDI, 5 speed, daily driver
1991 Ford F-350, work in progress
1984 Ford F-250 4x4, 6.9l turbo diesel, 5 speed manual
Previous oilburners: 1980 IH Scout, 1984 E-350, 1985 M-B 300D, 1979 M-B 300SD, 1983 M-B 300D
Spark-free since 1999

Not quite. That's true in the sense that a Kia is the same as a Mercedes, except for costing less. They're both transportation devices but the differences exceed the similarities. I hear Brown Bread isn't bad, but the Dynamat Xtreme should be quite a bit better. I think BB may be more comparable to the original Dynamat (which is thicker, less effective, and harder to shape/mold).