Has this been discussed? Engine bay sound pad Options

[rick 918-S]

I have decided to restore the Raspberry car as close to Concours as I can. I have an engine bay sound pad that is very nice. I mean really nice. One problem though. The pad is glued and held in place with plastic retainers. Over time, the pad holds moisture against the firewall and will cause rust. This actually happened to this car and the Ravenna car I have causing rust holes in the firewall. Here in MN we have cold wet winters and damp humid summers. It is very likely if I just do what the factory did to install the pad the process of rust will just start over.

My question is:

You guys that have completed a concours quality car must have thought about this. What have you done to prevent the creep of rust that starts behind the pad?

I'm working on a couple ideas that I think will work without causing the judges to freak out. I thought about trying bed liner. The stuff is near bullet proof in the bed of our Titan. I haven't even been able to scratch it. The glue that is used to secure the pad should not be able to penetrate the bed liner which is what I think is happening to the painted finish behind the pad. The glue will break down over time causing the loss of paint that it is stuck to. The moisture in the pad will start the rust process. The rest is history.

BTW: I would only be using this on the firewall and it will be completely hidden by the back pad. Cool? or Lame?

I also thought about thinning out some fibre glas resin with laquer thinner and carefully wetting the fiber that contacts the firewall. This way moisture would not be absorbed anymore. (IMG:style_emoticons/default/confused24.gif) just thinkin out loud.

[dr914@autoatlanta.com]

we install out dynamat new factory identical pad that does not hold water Dynamat made it for us under contract

[JeffBowlsby]

I like the idea of the fiberglass coating Rick. Just stick the backpad to it. Not sure about the bedliner...is it 100% waterproof or does it actually absorb moisture - check to see if its 'permeable', even just a very little bit. Avoid it if it is, even many waterperoofing materials absorb the tiniest amount of water, like 0.002%.

[rick 918-S]

we install out dynamat new factory identical pad that does not hold water Dynamat made it for us under contract

I'm always learning here. Cool.

[rick 918-S]

I like the idea of the fiberglass coating Rick. Just stick the backpad to it. Not sure about the bedliner...is it 100% waterproof or does it actually absorb moisture - check to see if its 'permeable', even just a very little bit. Avoid it if it is, even many waterperoofing materials absorb the tiniest amount of water, like 0.002%.

Ya, I agree, some coatings will allow moisture intrusion. I may ditch the factory for one of Georges replacement pads. Didn't know there was an option.

[Tom_T]

Hey Rick - you saw what happened to the firewall/engine lip on my 73 in those Body shop recco topic pix that I posted, & had it happen to yours.

I'm in the same quandry as you, but won't reuse my crappy pad. (IMG:style_emoticons/default/huh.gif)

I like what George is suggesting, but I'm not sure if it passes the CdE muster, or if some judge will gig pts. for it?
... George, any experience in competition with them? (IMG:style_emoticons/default/confused24.gif)

The other idea I toyed with - similar to your fiber-glassing resin idea - was to try to adhere a sheet of polyethylene or something to the inside face where the sisal fibers are bare. I think that the resin would soak in too much & not form a solid & waterproof barrier - at least not without loading tons of resin on it!

The truck bed liner on the firewall may be a good idea & is supposed to be more waterproof than under coating, but I think that leaving the adhesive off & only using the metal clips around the perimeter (top, bottom & sides) & the plastic nuts/clips (middle area) would be preferable.

For one, you can regularly remove it & check for problems if it's loose, & another is that the slight airspace may allow any moisture to drain & dry. If it won't stay flat right, then spots of adhesive in droop areas would be preferable to the full spray-on of the entire pad.

The other critical area in this problem is to make sure that the rain tray doesn't droop/sag between the 3 forward clips/straps, thereby allowing the inner waterfall onto the pad/firewall. This is less of a problem with the late trays due to the 2 stiffening ridges added to the bottom, but the early flat ones started to sag almost immediately due to the engine bay heat.

Mark/Mikey914 is thinking of doing a repro early tray for those of us with early 914's on which that is the correct part, & I've suggested that he use both thicker plastic in the tray, as well as to add some discrete stiffener along the front lip (or a yet thicker lip).

Hope this "thinking out loud" is helpful! (IMG:style_emoticons/default/biggrin.gif)

[96740]

When I was having my engine rebuilt I was seriously thinking of having that "Pad" removed. it was bugging me but I left it. How loud is it without it?

[rick 918-S]

Hey George, Gots any photos of your pad installed? Any experience with the concours police?

[watsonrx13]

we install out dynamat new factory identical pad that does not hold water Dynamat made it for us under contract

(IMG:style_emoticons/default/thisthreadisworthlesswithoutpics.gif)

-- Rob

[scotty b]

Rick, my concern with bedlining the wall first, would be how well will the glue bond ? You will end up with a hard " plastic " surface that has quite a bit of texture. Glue won;t like that combo. I would consider putting a layer of dynamat on first, then glueing the backpad to that. The dynamat will ( should ) provide a water tight barrier, seriously step up noise reduction, and will have a smooth rubbery surface the glue should bond to pretty well (IMG:style_emoticons/default/confused24.gif)

[Pat Garvey]

I have decided to restore the Raspberry car as close to Concours as I can. I have an engine bay sound pad that is very nice. I mean really nice. One problem though. The pad is glued and held in place with plastic retainers. Over time, the pad holds moisture against the firewall and will cause rust. This actually happened to this car and the Ravenna car I have causing rust holes in the firewall. Here in MN we have cold wet winters and damp humid summers. It is very likely if I just do what the factory did to install the pad the process of rust will just start over.

My question is:

You guys that have completed a concours quality car must have thought about this. What have you done to prevent the creep of rust that starts behind the pad?

I'm working on a couple ideas that I think will work without causing the judges to freak out. I thought about trying bed liner. The stuff is near bullet proof in the bed of our Titan. I haven't even been able to scratch it. The glue that is used to secure the pad should not be able to penetrate the bed liner which is what I think is happening to the painted finish behind the pad. The glue will break down over time causing the loss of paint that it is stuck to. The moisture in the pad will start the rust process. The rest is history.

BTW: I would only be using this on the firewall and it will be completely hidden by the back pad. Cool? or Lame?

I also thought about thinning out some fibre glas resin with laquer thinner and carefully wetting the fiber that contacts the firewall. This way moisture would not be absorbed anymore. (IMG:style_emoticons/default/confused24.gif) just thinkin out loud.

How about this - ditch it! This is one of those additions that I rate right up there with hydropneumatic struts on early 911E's (had one).

They were both poor designs. The struts were recognized by PCA as stupid, with conventional strut replacements considered OK & not a ding.. Same should apply to that stupid sound pad! Poor design & it accomplished virtually nothing.

Pull it off, clean up behind it, enjoy the noises.

It was a good idea, but poorly exercised.
Pat

[McMark]

Could you remove the 'hair' and glue what's left to some Second Skin Luxury Liner or other closed cell foam. Stock look without moisture retention.

[914werke]

I cleaned and cleaned and cleaned mine, then just used the plastic retaining "rivits" & the stock metal tabs to hold it to the firewall, no glue. Easy to remove and clean behind when required.