Floor Pan insulation W123
 

Once I get back home in April, one job will be to reinsulate the floor pans on my 85 300D.

I found that there are part numbers:
A1236822101 and A1236822001.

But it seems neither of these show up as in stock in USA. And, apparently, only driver side is available from Germany.

Too bad, it would have been nice to use the OE stuff.

I have some Dynamat like stuff. But it is not as thick as the MB lining. I looked at teh roof patch stuff at Lowes (Peel & Stick?) but it too is very thin.

Think that perhaps I will use the thin stuff I have to make a sort of tray to catch any water. And then make a carpet underpad using the HD black foam carpet underlay that they sell at Home Depot. It's about 5/16" thick.

Anyone done anything like that?

Not I, though I have been thinking about it. I would consider painting the whole floor pan with POR15 as a good starting point. You just can't let that oxidation get started underneath good padding and insulation. I do think POR15 would give you the protection necessary.

hi graham,
i myself have some of the adhesive butyl underlayment for this and similar jobs. i think the trick is to layer it up. it sticks pretty solid so putting down five layers should produce a pretty beefy layer of mass loading insulation.

cheers,
aaron.

I will definitely be using POR-15 (or the near equivalent currently sold at Napa stores in Canada). I have places on my 107 SL that I painted with POR-15 over 20 years ago and still good.

In some ways, I like the idea of not using the adhesive sound insuulation on the floor pans, just so the carpets can be lifted and the floor pan inspected. My SL is that way. It just has heavy insulation attached to the underside of the carpets.

yup, putting that stuff under the carpet does sound like a good way to go.

The stock MB deadening from the '70s and '80s was usually a combination of heavy pitch-like layer of "black stuff" topped with a 1/8" inch (or metric equivalent) of asphalt board.

The asphalt does very little for sound deadening, but does provide a bit of heat insulation.

I'm getting ready to remove and replace some of the insulation in the old 240D with a combination of the Dynaliner and Dynapad insulation. I also plan on lining the roof (no sunroof), doors, back seat pans and such.

I had rust even where the OE pitch like layer was adhered. It could not be inspected and as a result floorpan rusted right through. My thinking at present, is to forget using Dynamat type material that sticks to the floor pans. Just paint with several coats of POR and then build sound insulation into carpet underpads that are attached to the carpet.

It would be interesting to know how MB treat floorpans on more modern diesels.

The original tar pad asphalt pad that MB used 30 yrs ago was probably good for what was available at the time. and as the vehicles moved down the assy line, it was quick and easy to install.
Now 28 yrs for the 85`s and 36 yrs for the 77 W123 bodys, the stuff is old dry and brittle and has lost it original intended use.

I was in a 81 300D at PNP yesterday, and the pass side floor where it sloped up towards the Blower Motor area, the sound deadener stuff was all cracked and I could lift it out in pieces.

One problem with it is it traps any water under it becaue of voids under it eventually creating rust to start..

Dynamat from what I know, will form to the contours of the floor and create a better bearier that the original stuff.
There are also other products like the Dynamat. each one better that the other.

There are a number of products out there that do sound deadening and create a heat bearier. Lizard Skin is a spray on product, or I assume it could be painted on also.
LizardSkin® Spray-On Insulation | Lizardskin

I found this site a couple yrs ago and saved it, but seems some of the stuff isn`t there now.the guy is reinventing his site or whatever, but still some good info.
Sound Deadener Showdown - Your Source for Sound Deadening Products and Information

What ever product you use, make sure the surface area is clean. This Wax and Grease remover is a good product. Kleen-Strip Prep All.

http://i.ebayimg.com/00/s/MzA1WDIwMA..._id=8800005007

Hope this helps some.


Charlie

I prefer simple acetone. It eats adhesives and tar, and it's relatively inexpensive.... but it does destroy stickers and such as well, so be careful.

NB, do not conflate mass loading insulation (heavy stuff like asphalt and butyl) with sound absorbing insulation (thick stuff like fiber mats and closed cell foam). use the former to reduce the vibration of surfaces by lowering their resonant frequency, and the latter in spaces where you want to reduce the amplitude of sound waves.

...and the good thing about sound 'absorbing' insulation is that it is usually useful as a thermal insulation as well. Although your mileage will vary for given materials used.

So:
Mass loading insulation = frequency filtering
Sound absorbing insulation = amplitude dampening