The stock asphalt sound deadening material works fine for deadening sound, the problem is if your car ever gets wet inside it traps water against the floor panels and rusts them out. The floor panels have ribs stamped into them for strength which the asphalt material lays flat over these ribs creating pockets for water to collect in. If your car has ever had an interior water leak you should strongly consider removing the asphalt from the floors.

The asphalt can be removed using a heat gun and metal putty knife. My floors had rusted so badly that I had to cut out and replace a 1’ square panel on each side of the rear floors (in an otherwise rust free car). After the asphalt is removed you can use POR-15’s Marine Clean to remove the asphalt residue, then wire wheel the rusty areas and rust-proof the floors with POR 15.

I plan to try driving the car with no sound deadening material for awhile, but if it is too loud I will put a modern sound deadening material down on the floors. The new sound deadening material should be able to be pressed down into the ribs to prevent any water pockets in case of future interior water leaks.

Edit: Pictures added.

Picture 1: Removal of old Asphalt Mat
Picture 2: Asphalt Residue
Picture 3: After cleaning with Marine Clean
Picture 4: After painting with POR-15

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine