Interior Seam Sealing and Sound Deadening

With some spotty availability over Christmas break to work on the car, I decided that seam sealing the interior and sound deadening could be accomplished in small chunks. Seam sealing prevents water intrusion where panels meet together. It can be applied from a tube, like caulk, or with putty spreaders like body filler. In different areas of the car, I’ve mostly used the caulk approach. This involves squeezing the seam sealer onto the joint then “tooling” the material with a brush, putty knife or gloved finger. Not wanting to overdo or overthink this step, I chose to bypass step one and just use a gloved finger.

Barrier Bond Seam Sealer is a gray, fast drying, brushable seam sealer. Working straight from the can, with gloved hands (and rags handy), I scooped out seam sealer onto a finger and spread it across the joint in one step. This lessened the time of contorting myself in the small passenger compartment, especially in the footwells can be a literal pain. One thing to be aware of are little metal burrs as you tool the joint with your finger. It can be pretty easy to slice through the glove and your finger as you run it along even the smallest burr.

While the can states that you can paint the seam sealer after 60 minutes, I gave it a full day before breaking out the paint. The interior was wiped down with wax and grease remover then painted with Rustoleum rust converter spray paint which I find can go over just about anything. It looks so nice and clean with the freshly painted flat black paint, it’s almost a shame to cover it up!

With the interior painted, next up was applying the sound deadening. The MG Midget was a budget British sports car with no frills or extra expense put into materials. Many feel that they can benefit from the application of sound deadening. Sound deadening can stop road vibrations from causing thin sheet metal to sing at different frequencies. Applied to door panels, it can change the sound quality from a tinny/rattly slam to a quality clunk you hear from more expensive European cars.

Another benefit of the foil backed sound deadener is heat isolation. One thing I noticed about driving the MG is that you could gauge engine temperature with your feet. The exhaust of the 3TC engine runs next to the steering column and down and under the driver’s feet and legs. After driving a while, the heat radiates into the passenger compartment. While the exhaust may get its own heat shield, the hope is the that the sound deadening product will also cut down on the heat transfer.

I chose self-adhesive 80mil Siless Sound Deadening Mats. This product is a cost-effective alternative to the household Dynamat product which dominates in car audio circles. The product is a joy to work with and has no problem adhering in cold temperatures, even upside down. To apply, you simply cut to shape, peel off the backing and stick it to the metal. A roller is recommended to really work the mat onto the metal. The mat can be cut with regular scissors or a razor knife. For this installation, I did both. Scissors are great for the overall shape while the razor knife allows you to remove material after it’s in place. When using scissors, you’ll notice that the butyl will eventually gum up the blades, so have some mineral spirits on hand to clean them periodically.

Finally, I chose one additional step of applying foil tape to the seams. This helps the butyl not ooze out from behind the mat and stick to everything (such as the carpet that will go on top. The 36sq ft did nearly the entire passenger compartment but I need to order another box to finish this up and probably do the same to the trunk.