Noise Reduction

This note is a consolidation of information elsewhere on the site discussing the issue of noise reduction.

My car was NOISY! You can do a lot to solve the noise problem. There are some specific areas that helped the engine noise in my car.

  1. Install sound deadening material.
  2. Fix rattles in the doors.
  3. Replace broken rubber seals in rear quarter panels.
  4. Be sure the fan behind the generator is not interfering with the shroud. That can be very noisy. See here for instructions how to remove and replace the generator.

At the present time, engine noise is under control. The remaining problem is wind noise around the doors and windows. I have not tried to fix this problem yet.
651-361-06 Add sound dampening material from Dynamat. The Xtreme material is much better than their other products. It is easier to apply and much better damping. You should line the inside of the engine compartment. Remove any remnants of the original material. By now it is crumbling and could even get into the back of the engine. The inside of the car below the rear window is not too bad to access and treat.

After putting the Xtreme sound dampening on the fire wall in the engine compartment, add a replacement damping mat that you can get from your after market Porsche supplier. This will absorb high frequency noise in my experience. Update: This has been removed. See below

You can purchase the Dynamat materials at most places that sell car stereo equipment.

An alternate material is by made by B-Quiet, although I do not have any experience with it. It's advantage may be lower cost.
030301-227a The door panels come off easily allowing the inside of the doors to be treated to reduce noise. The original insulation had fallen off and was replaced with more Dynamat Xtreme material. The doors need to close properly to reduce wind noise. A bright metal strip had been installed backwards which prevented the driver's door from closing all the way.

Be sure the various adjustment holes around the edge of the doors have plugs installed to reduce a bit of wind noise.
651-361-07a The rear quarter window seals were bad from the beginning. It was not fun to fix them because the replacement rubber seals are not the correct shape, so installation was tedious. I waited a couple of months to fix the second, then was amazed at the difference in interior noise.

Replace the rubber seals around rear quarter windows. Many of the old cars I've seen have hard, brittle and broken rubber. Vibrating hard rubber pieces sounded like high frequency engine noise. I did not find a source for original cross-section rubber for my car, but gluing later seals with 3M Trim Cement is an acceptable alternative.

We were surprised at the improvement in the noise level this fix made after both windows were done. Engine noise at highway speeds is finally to an acceptable level. This is good news.

Update 12/31/01

I have not been happy with the foam insulation pad because it was never attached properly. It was ripped out today and replaced with another layer of Dynamat Xtreme sound insulation material as described above.
Last modified: Mon, 31 Dec 2001


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