Sound Deadening Your 4Runner - Part 3 - Deadening the Headliner
By: Bob_98SR5
Last Updated: August 4, 2003
Application: 1998 Toyota 4Runner SR5

Obligatory Disclaimer
I am providing this write up for illustrative purposes only. Perform at your own risk. Any mods (including this one) you perform on your vehicle is your responsibility. Commercial use of this write up will result in legal action as well as the undying scorn from members of the online Toyota 4Runner community. You've been warned.

Summary
Sound deadening will have one, immediate net effect: a quieter cabin. And a quieter cabin will allow you to hear your music better---but your girlfriend's nagging is...well, you know. ;) Ok, back to the write up!

Step 9: Deadening the Roof
The easiest part of your 4Runner to deaden (and practice on) is the roof. For the most part, the areas are large, flat and easily accesible. There are three large areas that can be deadened in a moonroof equipped 4Runner. Start by wiping down the area once again and measuring the each of the three areas with your tape measurer. Write down the dimensions of each, get a sheet of HTM, and move to your work table.

Using your measurements, cut both the HTM and carpet padding out for the rear and the middle sections. After cutting the pieces out, divide and cut them into three parts. The reason for doing this is that the HTM is heavy---the adhesive won't support the weight of one large piece. For the last, largest section next to the moonroof, only cut padding for the rear half of this section. Also, use smaller squares here in this section as it is a bit bigger than the other two.

From top to bottom, the rear, middle and front section		For deadening, use HTM in all areas. For the front section near the moonroof, use HTM only. Padding will prevent the moonroof cover from sliding backwards

Now you're ready to apply the padding (this is really fun). Spray a coat of 3M #90 Adhesive spray on the rear section as well as the back side of your carpet padding. No need to go hog wild because this some sticky stuff. Allow it both sprayed surfaces to dry for about 45 seconds to 1 minute. Then quickly manuever both pieces on. Finish this section and do the same for the next middle section.

For the front section near the moonroof, apply the carpet padding only to the rear-most part of the moonroof section. Putting padding in the front section will prevent the moonroof from sliding backwards.

Here's the HTM applied to the rear and middle sections		Here are all three sections with the HTM and the carpet padding applied. Notice that the moonroof section has carpet padding only in the rearmost portion of it.

Step 10: Deadening the Cargo and Cabin
You're now ready to move onto the cargo section. Take a hand broom and sweep the rear section of any dust. In this section, you'll notice alot of irregular surfaces. At first I was trying to form the HTM into these channels/grooves but after awhile, I just gave up. The HTM isn't very malleable but has the advantage of being thick. In anycase, cut large sections and cut/score where necessary. I applied HTM to the floor and the wheel well humps. Use the same methodology of applying the carpet padding to this rear section.

For the passenger section, use the same methodology as above. There are some sections on the front and rear passenger seats that won't accomodate both HTM and carpet padding. In fact, there are sections that won't accomodate the HTM either. See the pictures below.

Trying to form fit the HTM into these channels is an exercise in futility. Just get it as best as you can and be done with it.		There are only a few areas that can't have HTM and/or padding, namely on the rear passenger seats. Raise and lower those seats and you'll quickly figure out where.

A side note about the side rear cargo panels, roofline area, and the front roofline area: not worth it. In fact, putting HTM might prevent your trim piece and fasteners from fitting back into their respective holes. Here's a large picture of the finished headliner and floor:

As you can see, the majority of the areas have been HTM'd and padded with the exception of the roofline trim, side rear cargo panels, and the front roofline area.

As an added step, some people spray in "Great Stuff" into the headliner braces. I didn't and it sounds quiet without it.

Step 11: Refastening All Panels
Start with the headliner. Slide the headliner on top of the trim panels. Push all the way to the front, go to the front area, and start aligning the visor, dome light, etc holes in the trim panel to the actual holes. Fasten the moonroof trim to start and then re-fasten the grab handles. From there, fasten the dome lights, the rearview mirror, and the visors. Finally, fasten the four headliner fasteners in the rear cargo area.

Fasten the pillar panels and play special attention to aligning the snap fasteners. Above all else, do NOT pound the panels to fasten the fasteners! You will end up breaking them or worse, detaching them and then you'll spend the next 10 minutes trying to find it somewhere in the body or on the garage floor.

Learning Points Thus Far
There is some squeaking from the passenger area which is most noticeable when driving on rutty roads at low speeds. I have not been able to isolate it yet. I believe it is some fasteners that might have broken or mal-formed when I pulled them out. Nevertheless on the freeway, my 4Runner is much quieter than before. When the doors are done, I'm guessing that it'll be even more quiet.

NEXT PAGE - Sound Deadening the Doors

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