Introduction: Auto Sound Deadening - Part II - More Matting and Using Expanding Foam

In I showed initial steps I took to add some sound deadening to a diesel Ford Excursion. It's a loud car; the 7.3l diesel engine exhaust could definitely use some muffling.

In this -part II- I'll show how I laid self-adhesive aluminum/butyl mat over all the sheet metal in my car's cargo area. I covered that first layer of sound deadening material with a glued-down sheet of ensolite foam to absorb yet more sound energy.

I laid down a double sandwich of those same materials on the floor. Per advice from an expert, Rick McCallum of, doubly covering the floor will help most with blocking out sound from under the vehicle.

I also used expanding polyurethane foam to fill in some huge and undoubtedly resonant voids inside my truck's body panelling.

I understand that most people who go to this amount of effort with sound deadening do it for car audio reasons. My primary intent with this project is simply to quiet the interior of the car.

Step 1: After Cleaning and Prep (see Part I) I Laid Down Acoustic Deadening Mat.

I took out all interior trim up to the headliner, cleaned and prepped and then started covering all the exposed metal surfaces I could with acoustic deadening mat.

I used tools I already had on hand. I purchased sound deadening materials from and my local Ace Hardware store - please see for a full tools and materials listing & some costs. So far the total spend is a bit over $400 and many hours of work.

Here are the sound deadening materials I applied...

Step 2: After Applying Sticky Black Rubber & Aluminum Mat, Do It Some More.

I heartily recommend a product called Invisible Glove.

I bought mine on special order from a local Napa Auto Parts store for about $9 USD, and subsequently probably saved triple that on disposable gloves. Those gloves gooped up incredibly quickly while handling the butyl/aluminum sheet material.

Applying RAAMmat to the rear Dutch doors and left side panel area took multi-hour sessions. (I only went after one side panel in the cargo area because the other is taken up by a ginormous rear air conditioning system I had NO intention of messing with.)

Working the adhesive mat firmly on to all the contours of interior paneling was critical to quieting things down though.

Step 3: Progress on the First Layer of Aluminum/butyl Mat...

I planned only one layer of aluminum/butyl and one of ensolite foam for everything but the floor panels.

Step 4: Applying the Ensolite Foam Layer(s) Was *much* Faster!

Using quick rough measurements and the spray adhesive, applying an ensolite foam layer over the aluminum/butyl mat went relatively quickly.

Step 5: I Foamed Up All the Big, Big Voids.

The rear Dutch doors, left side and rear corner pillars of the Excursion's cargo area were all basically large and formerly echoing gaps. I filled them with expanding polyurethane foam - Great Stuff Large Gaps from Dow Chemical.

In the left rear Dutch door there was a lock mechanism to protect; I snipped open a couple of coffee pod tins and used those with some metal tape to create a barrier around the lock components. I wanted to prevent foam getting in that system and tried to preserve a path to access it for any future repairs or maintenance.

In the right side rear pillar there is one wire run. I only foamed up to just below the level of that wire bundle run so as to be able to remove it if necessary later. "Snot perfect, but hey. Tradeoffs.

Working with the Great Stuff foam I found a couple of ways I could have improved the process. I went through 6-8 cans of the foam by spraying it in to deep or very large gaps too quickly... could likely have used much less foam by being patient and letting each "course" expand, skin itself over and completely puff up before laying down another layer.

Step 6: Working the Foam...

The polyurethane foam I used was SUPER sticky when drying.

Even using Invisible Glove did nothing to keep my hands clean, and the day and a half after I'd done the first application of foam my hands were almost completely black.

Had to wait until the residue simply wore off my skin. Thereafter I wore disposable gloves when working with the wet foam.

The foam didn't dry consistently. Areas that were not exposed to air were still seeping and liquid even several days later. Initially I laid down a couple layers of loose paper towels to catch areas I knew would overflow, letting big foam waterfalls blop out the top of the tape dams I made to shape the largest gap fills.

Step 7: Tinpot Dictator.

The lefthand Dutch door has a lock assembly I needed to build a stronger barrier around... it's down in a corner and I wanted to preserve an access path to the assembly if needed in the future.

I used tin snips and a couple of old Illy coffee pod tins to build a strong wall to place around the base of the assembly, then taped that down on top of the butyl mat layer inside the door's well. I used more tape to close an airspace between the top of the new little metal wall and the inside panel of the door.

I foamed slowly and in gradual layers around this barrier wall to keep expansion of too much foam at once from crushing it. I spritzed my successive layers to help them skin more quickly and worked up to cover all around the lock's new snug home.

Step 8: Still to Come...

Still to come... replacing all cargo area trim pieces and getting fit & finish completely restored back there.

Then on to removing the 2nd row 60/40 split bench seat for more floor access, then

quieting the middle and the front doors, then

capping off with removing the front two seats and carpet for some whole-floor muffling action!

Followed by perhaps lining all removeable trim pieces with an ensolite layer.

And stuffing bundles of ensolite up into gaps inside and under the front dash,

and perhaps hugely ambitious foamed cell compartments created in areas of the undercarriage and against the exterior wheel wells' sheetmetal....

It may never stop. >:-)

Someday there will also be a 2-DIN Windows 7 touchscreen car PC install with wireless synching to the house systems. :-)