Roofing the inside of the 4Runner

"JCAlan" (jcalan) 04/26/2018 at 13:52 • Filed to: None

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I’ve always thought that 3rd gen 4Runners were heavy on road noise, even when they were brand new. I certainly feel that way about my !!!error: Indecipherable SUB-paragraph formatting!!! . So before I go swapping out that factory cassette player and dealer-installed accessory in-dash CD, I thought I’d see about improving things in the cabin a bit.

What I immediately found is holy shit, Dynamat is expensive! You would have a small fortune lining your ride in that stuff. So I found an alternative, which is an adhesive roofing patch product called !!!error: Indecipherable SUB-paragraph formatting!!! , that you can buy at Lowe’s for 17 bucks a roll. The internet is STRONGLY divided on the merits of using such a product for this application.

The arguments AGAINST its use include:

There really are no sound-deadening properties

The applications have nothing to do with each other, butyl construction vs asphalt adhesive are not comparable in any way

The fumes will be toxic

It will not adhere and will melt and fall over time making a huge mess

The arguments FOR its use are:

Meh, it’s basically the same

It’s cheaper

My thought is that it probably does nothing to absorb sound inside the car, since the inside-facing surface is smooth aluminum. But I don’t see why it wouldn’t help isolate sound from protruding into the car (my reason for use), because if nothing else it’s a layer of stuff between you and the noise. It also bonds everything together so it certainly should help prevent rattles. On one hand, the company itself makes absolutely no claims for sound deadening and does not list that as even a possible use of the product. But on the other hand, half of the reviews on Lowe’s are from people who have used it for that purpose and are satisfied. I figured, what the heck, I’ll give it a shot.

The first thing I realized while stripping out my interior is how much thought has already gone into sound deadening. Most of the surfaces have at least one, if not two layers of material on them already. The outer body panels have an absorbent material strategically placed on them, and the firewall has a large rubber and fiber insulator. There is a large rubber mat in the cargo area. I began to think that perhaps my efforts would be futile on top of what Toyota has already done.

!!! UNKNOWN CONTENT TYPE !!!

But what the system seems to me to be lacking is one solid uninterrupted layer of ...something (except the carpet). Since that’s essentially what I’m putting down, I still think it will improve. I intend to do the entire floor and behind the door panels. I would be hesitant to put it inside the doors or on the ceiling, although I’ve seen installs where they did and held up fine.

I’ll report back with results!

Daily Drives a Dragon - One Last Lap > JCAlan 04/26/2018 at 13:56

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I have a theory that it’s coming through the trans tunnel. But also I can’t prove it. Also the glass and steel seems really thin so that can’t help with wind noise either.

Wacko > JCAlan 04/26/2018 at 13:58

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I was going to ask to how it will react to the heat of a car, but if it’s on a roof it gets really hot there too. Just thinking that your car will smell like tar/roof every time it gets hot from the sun....

JCAlan > Wacko 04/26/2018 at 14:02

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We’ll see!

Wacko > JCAlan 04/26/2018 at 14:03

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smell you later

vicali > JCAlan 04/26/2018 at 14:10

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Myself, I’ve always liked the sound of roof racks and mud tires..

razorbeamteam > JCAlan 04/26/2018 at 14:15

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I used it on the floor of my Volvo 240 after extensive rust repair on that thing. I don’t remember the smell being too bad. I can’t comment on its sound deadening properties because the car was totaled very shortly after I finished. Now you’ve made me bring up painful memories, thanks a lot buddy. Where’s the bourbon...

RamblinRover Luxury-Yacht > JCAlan 04/26/2018 at 16:38

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Yes, asphalt ought to deaden sound. In fact, there is a material called tar board which is basically tar-impregnated cardboard that was used for ages. See here in the floor of a VW:

The foil layer is better thermally and to give the material cohesion than for sound, obviously.

Butyl is better, obviously, and tar that’s able to leach out of materials can promote rust, which is bad, but it’s a thing that’s been done.

Yotarocket > Wacko 04/26/2018 at 20:11

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I’ve used it. Lined the inside doors of a 3rd gen 4runner and it never smelled. Even in 100+ degree heat there was still no odor.

Ready for an adventure! > vicali 04/26/2018 at 20:52

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is your real name David Tracy?

itranthelasttimeiparkedit > Wacko 04/26/2018 at 22:33

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Yeah I will never do dynamat again. Did 2 cars in high school, smelled like shit in the houston heat

vicali > Ready for an adventure! 04/27/2018 at 00:08

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Haha- he likes the sound of hot wind blowing through his rad and part falling off his heeps.. my kind of rig goes to Ushuaia and back like it’s no thing. 

GLiddy > JCAlan 04/27/2018 at 00:18

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Search for Noico 80 mil sound deadening material. Not cheap but cheaper than Dynamat. I thought about the roofing material, but didn’t want to worry about breathing asphalt fumes.

adamftw > JCAlan 04/27/2018 at 07:44

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Mass absorbs sound. It’s basic acoustics. I used Peel and Seal on the inside of my bifold doors in my laundry room closet and it made a HUGE difference. Like 8db IIRC.

Whenever the headliners come off any of my cars I always added it and it definitely made a difference. Never had an issue with it melting off either, but I live in the northeast so YMMV.

Party-vi > JCAlan 04/27/2018 at 08:09

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Oh man. If the car already had that much CLD you would have been better off putting down a layer of foam and then some MLV product, something that weighs 1lb/sf. Make sure you cover the wheel wells and get behind the doors too. At some point your windows will be the only weak link in your plan. Also, think about removing the headliner and tossing some peal and seal up there. You’d be amazed at the difference a damped roof makes, especially for rain.