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.

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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. :-)

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    12 Discussions


    10 years ago on Introduction

    You can also use roofing patch material.  It's basically the same thing.  Get it at HD or Lowe's. 

    You used far more foam than you needed to.  All you have to do is dampen the vibrations on the big flat(ish) metal panels.  The obvious big panels are the trunk and the hood.  The side and door panels come next and the roof if you can get to it.  The flooring is a big panel but it is usually formed to stiffen it.  All you need to do is stick a couple strips of of the aluminized tar paper or a couple lines of foam in an X pattern.  What you did will work but it's just a waste of foam. 

    Another approach would be to use a heavy adhesive like that used to hold lineolium flooring down.  Apply it with a slotted adhesive trowel.  This would leave the panel covered with a pattern of stripes.  When they dry they will help damp the vibrations across the entire panel or where you can reach. 

    4 replies

    Reply 4 years ago on Introduction

    Applying Roof Strips from Home Depot cost me about 450 bucks and more time than I care to spend. After I did damn near my whole exvursion, it got hot in town and that stuff was off cgassing like hell. Do you have ANY ($&%Y#W*@) IDEA HOw hard it was to remove it from the entire floor, all four doors? Took two mexicans two days, and my wife and I another two days, then about another 4-6 days of cleaning TAR crap off the car. Not to mention I had to find something that wouldn't kill us to clean it. If you value your time and life - don't use a roofing product - PERIOD. Oh, I had to clean and relay all the sound deadner twice becuase someone sauid - yeah it's all the same - Negative. Asphalt is Tar based. BUTYL is rubber and has no residual.


    Reply 4 years ago on Introduction

    Sorry - didn't mean to go crazy, just it was a bad move. This truck is moslty for families and don't want to kill our kids with poisoinous gasses. Maybe for a 20 year old with a civic, but doesn't do justive for the X. I think you are right on the Expanding Foam. I did not fdo that in mine as I felt I wanted to keep only automotive products in mine. I used SEM auto Sealer for all joints int he car and really went overboard in compared to yours. After I did the Asphalt and then ripped it all out, we cleaned the tuck dowbn, but to remove the tar, it took all the caulking and factory sound proofing out. So I recaulked all corners, etc with the SEM Seam Sealer (AWESOME Stuff!) then went with a liquid lay down of GT Sound Control Liquid Sound Control, then TWO layers of 80 MIL Butyl, then another layer of liquid. I also notice my excursion did not have the insulation pieces over the wheel wells, so I went to a junkyard and got those. I moved the AC, did behind there, added close cell foam, etc... Ugh... It has been 7 months. My wife wants her truck back.

    This all started with - Honey, can you put speakers in the truck!


    Reply 10 years ago on Introduction

    Thanks for the comment - but with respect, roofing patch material is NOT the same thing. As you note, it's tar based- as a result, it stinks mightily and will melt & possibly slip around in very hot weather.

    I agree that it could be used, as could tile mastic or other flooring adhesives, and I've read at least one writeup that mentions someone having used roofing tar sheets extensively. Probably would have been much cheaper than what I used...

    But, but, but - the RAAMmat I used is specifically designed for auto sound deadening. There was very, very little odor, and it's tacky butyl rubber with an adhesive layer under soft aluminum composition won't melt and run or possibly even slide completely off in hot weather. We regularly have summertime heat reaching 110+ for weeks on end where I live, so that was a big consideration.

    I hear the "too much foam" part of your comment tho, and I completely agree. :-\

     I was however trying for *as much sound prevention as possible*, and I think the overfoamkill and completely covering all panelling with at least two deadening mat layers is definitely accomplishing that. Panels and areas filled with it sound *solid* when knocked on now, versus a hollow echoing tap coming back from unfilled areas.

    I'll run out of materials before I can get to it, but the roof and panels inside the engine compartment like the hood are likely suspects for future parts of this extended project.

    Thanks again for your comment - good ideas and alternatives!


    Reply 7 years ago on Introduction

    I worked for an appliance store many years ago. Whenever they bought a new van, they'd apply mastic to the floor, then stick cut-to-fit 1/2" plywood to it. They did it to strengthen the floor, but I'm sure it quieted the vans down as well.


    4 years ago on Introduction

    This is awesome, thanks so much for your photos & comments in the photos. Do you think the spray foam made a significant impact on sound reduction? Once the aluminum/butyl mat and the ensolite foam is applied, I'm wondering whether it's a matter of diminishing returns when applying the spray foam? Given the amount of effort required on the spray foam, do you think it was worth it, in terms of additional sound reduction?


    5 years ago on Introduction

    Definitely a worth project. Have you finished it yet?


    5 years ago on Introduction

    Thanks for the instruction. I am about to do something similar with my 81 1.9l turbo diesel AAZ swap VW Truck as well as my 77 TDI swapped Rabbit!
    I beleive I may go with #2 marine foam, though.


    8 years ago on Introduction

    HILTI makes a foam product that might work better in this project. First it is hydrophilic, and cures by sucking moisture from the air. Second, you have about a month to use the can- instead of about an hour with the Dow brand. This means you can put layers down and not worry about buckling panels.

    You can get it through Hilti, or you can get it at home depot. It's called cf116. Home depot only carries it on the shelves in larger stores. The other stores can order it through the pro desk or you can check home depot online.


    9 years ago on Step 1

    expanding foam will just trap moisture and create rust i just had to replace the rocker panels on my truck because the previous owner thought great stuff would be somehow helpful inside the truck. the foam came out shaped like the inside of the panels and the panels fell apart in my hands. i was reading today about some marine stuff that they use for soundproofing motor covers on boats. something like that might work well. and be cheaper then the brand name automotive stuff.


    9 years ago on Introduction

    i'm interested in your sound deaadening project on the ford diesel.  i have a similar ford diesel.  it too is very noisy, 95dbs going down the highway at 60mph.  did you check the dbs of your ford before and after you finished the project?  i would really like to know how successful you were at reducing the dbs at free way speeds.  i'm not into doing the project myself and upholstery shops cost a lot and have no before and after comparisons.  i would really like to know it is going to help before i spend a lot of $.  regards bob

    1 reply

    Reply 9 years ago on Introduction

    I can't offer before/after decibel readings, unfortunately - I don't have a sound meter.

    Just doing the cargo area and rear side panels yielded "noticeable" results, if that subjective analysis does you any good. '-) I feel strongly that even the project so far has been very well worth the effort.

    I haven't had time yet to complete the project with deadening under the 2nd row seating and forward; so far I only also have the left rear passenger door sound insulated. Given how much quieter the rear of the car is now I'm really looking forward to getting the remaining floor and doors done.

    Watch out for keeping lock rod travel clear when doing doors... Mine is sticking somewhat on remote control, tho manual operation is fine, and I've got to get back in to free it.