TECH TIP Technical Index

Interior Upgrades – Tech Article #2

by Mike C. -

Sound Deadening

After putting sound deadening in and around the engine compartment and rear luggage area, you should be able to hear yourself think while on your way home from the bratwurst burger joint. But now it’s starting to rain pretty hard and the roof sounds like the tin roof on a barn or country cabin when it’s raining. Well, time for project number two! This time I’ll cover the roof and floor pans.

Tap on the roof. Sounds like a drum, doesn’t it? We’re about to change that.

  1. Clean the inside of the roof thoroughly with wax and grease remover.
  2. Cut a large piece of the asphalt sheet and stick it to the inside surface. Make sure the sheet is stuck very well or it will tend to come down when it gets hot. An option is to use Dynamat’s super thin dampening sheets that are good up to 300° .
  3. Now spray some adhesive on the surface of the sheet that is already stuck to the roof and stick the jute padding on it.
  4. Finish up with an asphalt sheet. Now go tap on the roof. Instead of ponnng ponnng, it goes thunk thunk! Now it can rain two feet a minute and you won’t hear it while you are driving in it. Plus, the sound deadening gets rid of the drumming effect inside the car.

Going on to the floor…

Remember, the more junk you remove from the floor pans, the better the job will be. If you saved your old tar boards or carpet, you can use these as templates from which to cut the sound deadening material.

  1. As in the past article, make a sandwich using asphalt sheet, jute padding, then asphalt sheet.
  2. Cut your asphalt sheet to fit each section of the floor pan and then stick it on. Be sure to push the sheet down in all the irregularities in the floor pan. Remember, the better it conforms, the better it will perform.
  3. The center tunnel usually has asphalt sheet stuck to it from the factory, so it will save you a step here if you didn’t remove it earlier.
  4. Also cover the kick panels on each side with the asphalt sheet.
  5. Then go through the routine with the jute padding on top of all this, and then a final layer of asphalt sheet.
  6. Now you can put your carpet all in and never know there is a load of sound deadening below, except you won’t hear nearly as much road noise as before.
  7. You can get even more trick here by getting a few cans of rubberized undercoating and spraying a heavy layer on the outside of the floor pans under the car. No noise here! Plus, it will protect the floor pans from thrown rocks and moisture. Don’t coat anything else, or it will make it a mess to work on the car.
  8. Finally, we’ll tackle the inner rear quarter panels and inner door panels.

  9. For the rear quarters, cut a piece of asphalt sheet to fit the area. Then jute padding, then asphalt sheet again.
  10. As for the doors, all the area from the bottom of the inner door beam to about three inches from the bottom of the door will be covered using the asphalt – jute – asphalt method.
  11. Getting trick here would involve a can of expanding foam and spraying it between the door beam and the door skin. This step will dampen the door so well that it closes very much like a New Beetle door.
  12. Anywhere you have two pieces of metal, no more than ¾ inch apart, this will work. Make sure that it is not in direct contact with water all the time, or it may create a rust problem.

There is only one area that old VW’s don’t fare well in is the wind noise department. Unfortunately, I don’t know of a simple way to solve this problem without much experimentation and probably massive body modifications. The only simple solution might be to replace the stock vent window and door glass with one of those one-piece glass kits. Anytime you can create a smooth surface for airflow, you will reduce wind noise. Also, some folks have found a way to flush-mount the rear quarter windows, especially the pop-out variety. Anyone have some information or comments on this?

Now you can install that Rolls Royce body kit and really mean it with a VW that is quiet enough to pass for a new car. Does Sonic have bratwurst burger deals?

Your VW Maniac and tech specialist,

Mike C.