SteveE400

To make a long story short, I drove a 2001 Lexus LS430 for about 15 years. It was a very quiet car, with adequate performance.

Fast forward to summer, 2015. Lexus was definitely long of tooth, and I replaced it with a new E400 4Matic sedan. So summarize my comparison. . . MB performance much faster than Lexus, but at the expense of much, much more road and tire noise.

I had the dealer and my favorite body shop (MB Certified) check all the door seals, etc., looking for anywhere the noises could be coming into the cabin. Found nothing. Car is just noisier. Lots of tire-slapping and frying bacon noise from tire treads. To me, this was out of character - even for a sportier model of the MB.

I've seen the postings here about those who coated their under-body panels with various sound-deadening preparations, and that seemed like way too much work for my issue. I have only stock HK sound system, so bass is not vibrating the car (yeah, right. . . ). I just hated the tire noise.

I decided to try a trick I had used on a VW Rabbit (remember those?) back in the late 1970's. I purchased some generic home insulation, in roll form. 2 to 3 inches thick, 18 inches wide, in 4-foot lengths. I removed the spare tire from the well and laid two strips of the insulation, side by side, to cover the entire well floor and up the sides. I then replaced the tire and tool caddy. After that, I rolled out two more strips of the insulation on top of the tire, covering all but the auxiliary battery and electronics. Then I just closed the trunk floor and trunk.

When I took the car out after this, I was simply amazed! My E400 is now almost as quiet as that old LS430. Almost NO tire and road noise - in town and on the highway. Yes, the exhaust sounds a bit more muted, but truthfully the exhaust sound of the TT V6 isn't all that exciting anyway. This little "fix" only cost about $20 retail, adds literally no weight to the car, does not affect performance, but soaks up a huge percentage of the road/tire noise -- and it can be reversed at any time with no leftovers.

I recommend this "hack" to anyone who feels that their car is just a bit too noisy. I don't see any downside. . .

raja777m

just muting the trunk is enough? cool, I know how I'll spend my upcoming weekend.

If it is something u purchased online, share the link pls.

I recently some some thread in this forum, which needs lots of elbow grease and might need some help of tools which I don't have. If this is just trunk, that would be a great start for me anyway

KEY08

Home insulation as in FIBERGLAS insulation? Yowza

Mud

I've used QuikRoof (Lowes/HF) on a number of restorations. I like the adhesion and thin layering. Even after several years in hot TX climate no petro smell or offgassing. I plan to use it in my benz as well.
I agree that these cars can benefit from a bit of added insulation/sound deadening.

djdirty76

SteveE400

I'm not at a place where I can "do" photos right now.

The insulation I used is the fiberglass roll-stock sold for insulating between studs of a sheet-rock wall. Plain and simple. I bought small rolls that were sold as being suitable for touch-up insulation around air conditioners, doors, windows, etc. You could also buy a whole roll of the stuff, and maybe even save a few dollars. The standard size is about 4 inches thick and 16-18 inches wide by some length. It is totally compressible, weighs literally nothing, and is easily cut with a scissors. I did mine over a couple of days, just because I was installing it over lunch time at work.

The other place where I can believe some unwanted sound enters the passenger cabin in these cars is through the rear seat backs. If the seats can fold down, they do not seal tightly to close off the trunk area. Thus, any noise allowed into the trunk has a good chance to get into the cabin as well. With the way the tire well insulation has helped, though, I am not chasing the seat backs for additional help. . . yet.

ghlkal

Interesting ... thanks for sharing. I will need to try this and see what happens.

DFWdude

Is there a modern replacement for fiberglass that can be used in this application? I agree that the fold-down rear seats are not completely sealed, and thus, my concern is that small bits of fiberglass can get into the air circulation system. I don't need fiberglass in my lungs.

bachree

Is this similar to what you used?
https://www.lowes.com/pd/Johns-Manvi...2-ft-L/3032423

SteveE400

Yes, bachree, that is the stuff. Anything similar to this would work, I'm sure.

DFWDude - I really don't see how anything from your spare tire well is going to get into the air supply to the passenger compartment. There is no intentional air circulation in the tire well, and no real air circulation from the trunk into the car. If there was, your car would have to air condition the trunk all summer. If you are worried, just cover the entire tire well with a sheet of plastic film or a dropcloth before you close it up. I would be more concerned if I was trying to use this stuff inside the passenger compartment, but under the trunk floor, I'm not worried. Don't forget -- this stuff is probably inside all the walls of your house. . .

Sunnyslope48

Yes, there is. And sound dampening qualities are MUCH BETTER.
https://www.lowes.com/search?searchT...ool+insulation

LALALAND

Not fiberglass or wool insulation, but I place 2 yoga mat on top of the tire and tool caddy. It's much thinner, but is it as effective as insulation mat? I have no idea.

DFWdude

Now THAT is an interesting idea. Good out-of-box thinking.

KEY08

Shove some old blankets in there, as long as we are going full Macgyver.

DFWdude

This entire thread is about MacGyverism. Since a 130 year-old company has decided a non-lined, bare metal trunk floor won't transmit sound to the passenger's compartment, it's customers are left to their own devices.

(BTW, my 2001 C320 does not have a bare metal trunk floor, but a blow-molded plastic liner that covers the entire area... the spare tire, etc sits on top of this liner.)

The question is what devices are the safest to use. If it were a simple matter of lining the area with insulation and replacing the cover mat -- never to be seen again -- then almost anything can be used that absorbs sound and vibration, including fiberglass.

However, experience tells me that I periodically need to open this area to store and retrieve things (spare tire mtce, rear battery mtce, access to tools, tire pump, etc). Invariably when done in this area, I let the floormat freely fall back into place, shooting dust and what-not in all directions. Accordingly, I want a safe material that holds together and is easily removable when needed. Just my opinion, but fiberglass doesn't do it for me.

SteveE400

Well, folks. . . if you don't like my choice of materials, feel free to improvise on my improvisation. In my case, that well is Never used. My last car was in the family for 15 years, and the spare was never on the ground. I do not store anything in the tire well, and in the MB it is only opened for service. Fiberglass down there just doesn't light my risk light. If you don't want to use the fiberglass (which homeowners have used for decades), then don't. I do appreciate the discussion, but I have no personal emotional investment in which material anyone uses 9so I won't take it personally if you choose another material).

I'm only trying to point out the relative benefit to be had from applying ANY sort of sound absorption material down in that plastic well. That a car manufacturer would expect that the total lack of insulation in that location is an appropriate design. . . well, in my opinion that is just the bean-counters saving a few cents per car, and it aggravates me. I had a W201 for many years, and that car was over-engineered and over-built. This one costs twice as much, yet they cut corners.

I guess I should not be surprised. I have worked for an automotive supplier for the past 20 years, so I know how the component manufacturing businesses are managed. Price is not the only thing they consider, but it is FAR ahead of whatever is number two.

DFWdude

Please do not take my posts negatively. I really do appreciate your pointing out the benefit of applying any sound absorption in the area. I've been in the trunk numerous times, and had -- until now -- completely ignored the bare metal finish, which could obviously use some improvement. Now that you have pointed this out, I will find some material to line the area.

I don't find the lack of material that obviously noisy, because the rock music I enjoy usually blocks most any road noise. I've read the other threads about applying very expensive auto products like dynamat, etc. but the process involved sounds too obsessive to me. But your idea of using common materials has opened my eyes to the possibilities, and I appreciate it. It's all good, thanks.

KEY08

SteveE400

Hey, DFWDude - No offense was taken! I'm sorry if I came across as if I was hurt. I wasn't at all. I just forgot to turn on my emoji to clearly indicate my snarkiness! I was "playing" hurt and hoped you would catch my drift. Sorry for the mis-direction.

In any of my comments, I have no inflated sense of emotional investment in an idea or comment. If someone has an idea to improve upon my initial thoughts, then we all benefit. I've even been shown to be completely wrong a time or two, and I'm still here. I often, though, revert to my sandbox manners, expecting that others will clearly sense my attempts at humor. Sometimes it works, sometimes not.

We're fine, and I appreciate your comments. If you do choose to go with the rock wool, do tell us how it works out. I thought about rock wool, but one of the drivers in my decision was which materials could be purchased without having to buy enough to insulate 6 or 8 cars. The stores where I shopped only carried large bundles of rock wool batts, at about $65/bundle. I wasn't going to risk that much money to test an idea.

For those who mentioned Dynamat or similar materials often used by the car audio guru's, I think the DynaMat serves a different purpose than simple rock wool or fiberglass. The DynaMat deadens vibrations of the metal or plastic panels of the car. This is most often sought when the owner has installed a high-power sound system with super-heavy bass capabilities. With these systems in our cars, the large metal/plastic panels of the trunk, doors, fenders and even the floor pan can exhibit "sympathetic vibrations" along with the bass of the sound system. These unwanted resonances can distort the sound of the music and wreak havoc with the general sense of calm in the car. By deadening the sympathetic vibrations using DynaMat, the system is back to playing only the notes it is supposed to play. I had to use DynaMat in my Lexus LS430 when I added the 500-watt amp and new after-market sub to the stereo. DynaMat works for resonance control, but I don't know if it does as good a job at simple noise/sound absorption as the rock wool or fiberglass do. Much as I'd like to add a kilowatt amp and a couple of subs to the HK system in my E400, I am not up to the design task with the digital and fiber optic systems in the cars. I also want to give the dealer NO reason to ever deny a warranty claim because some wire I installed did something, which did something else to another component, which hurt something else. . . and nine steps later caused some catastrophe that should be warrantied, but they wiggle out because I added some little wire somewhere.

Now, once the car is out of warranty, all bets are off.

MBNUT1

Guess I surprised that insulating the spare tire well would be so impactful. Would have thought you would have had to go after the wheel wells. Good to know.

marathonrunner

Anybody look at Neoprene Sponge Foam Rubber Sheet Roll (Ebay or Amazon): WATERPROOF & NON-ABSORBENT - Made from Neoprene Sponge Foam, this material is specifically made and designed to repel liquids and odors. Perfect for high traffic areas such as auto, garage, and kitchen areas. PROTECTIVE - The ¼" thick dense sponge foam is perfect for providing cushion or padding. Easy and economical solution for sealing or insulation projects. Great for noise insulation and sound vibration reduction. ADJUSTABLE & FLEXIBLE- The Neoprene Sponge Foam Sheet Roll is strong enough to withstand tearing but easy enough to customize and cut to size with scissors or blade. Will bend easily and conform to any shape. DYI & PROJECTS - Use around the home or workplace to provide custom padding or insulation solutions.

Comes in a variety of thicknesses and sizes. With or without adhesive on one side. I'm only a month into a "new to me" 2014 E350 sport. But I'm probably going to give it a try and I can report back if I notice a difference. Seems like a good material for the trunk, if it works.

raja777m

Might get the adhesive version:

Seems a bit expensive, but should be worth it.
If you're pulling the plug, let us know the length of the sheets we need to buy. I may start with one now. Need to work over the weekend.
Thanks.

marathonrunner

That's about what it seems to run. And it can go up from there. This is the non-adhesive version I was looking at, it's a little bigger, and it probably comes in a version with the adhesive: https://www.ebay.com/itm/Neoprene-Sp...4AAOSwjXNa-Fg1

marathonrunner

I found this place that seems to have pretty good prices and other options: https://www.foambymail.com/
Didn't look like any of the foam had adhesive on the back, but you could use the 3M Super 77 spray adhesive if needed.

Sarang

i really liked this. thanks for the tip