Remove or keep rear seat soundproofing ?

[Recycler]

All front floor pans are now clean to the metal. However, old rear seat floor pans are in great shape (zero rust) and debating on removing or keeping the old soundproofing ??

I will be recovering with Dynamat to cover all areas. The rear seat area will end up being doubled if I keep existing bitumen. Beside the weight issue, is the another primary reason to not keep the old soundproofing ?

 

Thanks

Steve

72 Sahara

74 Golf

[joysterm]

I know its a real PIA to remove but I'd take it out if I was given the same predicament. I used dry ice on mine which made it  easier. 

[Buckeye]

Do not disturb it if there is no sing or rust. 

[esty]

leave it...it was put there for a good reason

[AceAndrew]

My car had “zero rust” visible around the rear seat area.  However, underneath the lower parts there was a small amount of surface corrosion from some long ago leak.  The water slid down the backside of the counter gaps in the deadening.  

 

Therefore, at least pull up the bottom areas for supreme peace of mind.

[VWJake]

Just take it out. You’re going to add new attenuator to car anyway. What’s an extra $20 in materials to replace the original when you prove it truly is rust free? I thought my 73 was clean back there. Turns out the blister I saw  from underneath wasn’t just a surface wound. It went clean through when forced.

[NYNick]

Do the floors (moisture), leave the back. Soundproof over both areas. No big deal.

FWIW, I left my soundproofing loose on the floor except where it had to be glued (tunnel etc). I like to be able to get under there if I need/want to. I used a MLV floor mat from HD. Dynamat is overrated, overdone and expensive IMO, but what do I know?

[Conserv]

I believe the answer depends on (a.) the facts that apply to your car and (b.) your goals for the car. The decisions are very personal.

 

I, for instance, value originality, stock appearances — notice I’ve emphasized “appearances“ — and a period driving experience. I’m not looking for a classic car that sounds and drives like a 2020 model. Dynamat, for instance, would not find a way into any classic car I owned. I appreciate, however, that a majority of classic car owners probably want their cars to be improved versions of the originals. And I get that. I feel that urge, too.

 

My ‘76 is currently wearing tii struts and calipers, a 3.64 LSD from a 1978 e21, 123Ignition — the latter concealed within a correct period housing (sorry Tom!) — and a Spal auxiliary fan much more powerful and efficient than the original Clardy fan. I suppose what these have in common is that they are simple “Bolt-on, bolt-off” modifications. I’m guessing that plays a key role in what I personally find an acceptable modification. The original components are in plastic tubs in my basement.

 

But that miserable original bituminous sound deadening — cheap, no doubt — is, to me, quintessential ‘60’s car. And, along with those chunky cardboard-esque under-carpet pads — cheap, no doubt — it gets the job done: ‘60’s or ‘70’s style! My ‘02’s are not recording studios. Heck, I almost never talk on a phone while in my ‘02’s: they’re too damn noisy.
 

With all of this said, on the issue of the sound-deadening, I chose to leave it in place on the ‘76, and I suspect I’ll reach the same conclusion on the ‘73. Heck, I’m proud of my original carpet and headliner. So... what about the rust? In the case of my two cars, there is no sign of rust on the exterior of the floor panels. And, there is no rust visible on the interior of the floor panels, in the areas left exposed by the factory. Could there be, as Andrew experienced, rust under the sound-deadening? Absolutely!

 

I recall the rainy (and, no doubt, beery) night I drove my ‘76 into a flooded underpass. The car stalled, would not restart, and water started coming in “over the gunwales”. I walked the car out of the “puddle” with the starter, dried out the distributor cap, and we bailed the interior with our shoes — never saw that pair of Clarks again! I pulled out the carpeting the next day and the car sat with windows and doors open for a week. So, yes, there could theoretically be corrosion under the sound-deadening, if (a.) the water got in there, (b.) found bare metal, and (c.) stayed in there. But if corrosion hasn’t appeared on the exterior, or on exposed interior metal, after 44 years, I’m guessing it won’t appear in the next 44 years, especially as my car is garaged and rarely driven in rain.

 

So, I leave the sound-deadening in place, based on my cars’ facts and my personal viewpoint about classic cars, a viewpoint which informs my goals for my cars. Each owner gets the opportunity to make his or her personal decisions.

 

Below: Some photos of the ‘76 with the carpeting removed.

 

Regards,

 

Steve

 

 

Edited April 6, 2020 by Conserv

[Mike Self]

What Steve said, with one caveat.  At the very leading edge of the floor tar sheet--closest to the rear seat cushion riser--chip away a half inch or so, especially at the outer edges closest to the car's sides.  If the backlight or quarter windows ever leaked, that's where the water is gonna pool. 

 

You might also look under the car at the hollow wedge-shaped brackets that help support the rear subframe, and poke around that same spot on the inside.  Moisture inside the brackets on my '69 rusted through the floor.  I caught it in time, thoroughly rustproofed the whole area and then covered the holes in the floor with duct tape so I can inspect the brackets' innards periodically.

 

Otherwise, leave the sound deadening in place.  And you'd be better off (especially financially) to stuff the area under the back seat cushion with either several sheets of styrofoam insulation cut to fit or closed cell foam--heck, you can use plastic bags of styrofoam peanuts--for sound deadening.  That space under the seat is an excellent sound board and will magnify any sound coming from the driveshaft and diff.   

 

mike

[iinca]

^I agree...and

 

I say don't rely on Dynamat products to kill sound. It will KILL vibration but does an average 

job at killing sound. Plus it's HEAVY! 

 

 FOAM does a much better job. Together the 2 products will actually make

a difference

[Recycler]

Thank you to all who posted their comments !

 

After a deeper forensic audit of the rear seat floors, the original sound deadening will be kept in place. I have a lot of experience working with closed cell foam so that is a viable detail to add on top of the new anti vibration/sound sheets. Dymamat was just a generic term I used and definitely not my first choice so will do more research on MLV from HD, Noico, Fatmat and other product lines.

 

Cheers,

Steve

[NYNick]

10 minutes ago, Recycler said:

Thank you to all who posted their comments !

 

After a deeper forensic audit of the rear seat floors, the original sound deadening will be kept in place. I have a lot of experience working with closed cell foam so that is a viable detail to add on top of the new anti vibration/sound sheets. Dymamat was just a generic term I used and definitely not my first choice so will do more research on MLV from HD, Noico, Fatmat and other product lines.

 

Cheers,

Steve

Unsure how much I paid for this MLV floor mat from HD, but knowing me, it wasn't a lot.