Rear fender foam, replace or other? Options

[bbrock]

I know this has been discussed before but wonder what current consensus it. I stripped out the seam sealer and urethane foam that fills the cavity near the tail lights at the rear of the quarter panels yesterday. Happy to say everything looks pristine inside. That cavity looks like a serious mud catcher and given that there are 3 miles of dirt road between my house and pavement, I'm not comfortable leaving it open. I'm thinking of filling it with Evercoat Sealant Foam after epoxy primer and then sealing like the factory did. Any better options?

(IMG:http://www.914world.com/bbs2/uploads_offsite/www.evercoat.com-20845-1534691900.1.jpg)

[bbrock]

Thanks all. I'm liking those liners. I think those would be a very good idea here.

I share everyone's aversion to the foam, but in this particular cavity, I cannot say the factory was wrong. I don't know how many have poked around in that spot, but this area forms narrow cavities that extend back about 8 inches to the rear corners of the car. You might be able to get away with leaving them open in a mild climate driving only on paved roads, but in my situation, I can guarantee they will soon fill with dirt and crud to form a moisture trap way worse than the foam with seam sealer ever presented. I live 3 miles down a dirt road so every trip will include a minimum of 6 miles of dust swirling around under the fenders and settling into those cavities where it would be difficult to impossible to clean out. I think the fender liners will help reduce, but not eliminate that. And if the swirling dust isn't enough, the cavities are the perfect size for mason bees and wasps to pack with mud tubes for their nests. I'm convinced that not closing that cavity would be a mistake.

My question is more about what is the best way to close the cavity than about whether to close it. The next question is how best to close it. The factory filled the cavity with foam to provide a backing for seam sealer which was applied over the foam. This worked fine until the sealer dried out, shrank, and cracked to let moisture in where it got trapped by the foam. This was one of the few areas that wasn't rusted on my car, so it worked for 40 years. I've gotta believe that sealer, and maybe foam has improved over the years since these cars were built.

Right now, I can think of a couple ways to close the cavity. One is to just replicate what the factory did with modern foam and sealer. Then add inspecting the sealer in that area to my annual maintenance schedule. The other is to cut a plastic disc to block off the opening and form a backer for applying sealer, then drill a small weep hole after the sealer has cured. That would leave the cavity hollow inside but prevent crap from getting inside. I'm kinda liking this second option but need to think about it more.

Before closing, I will treat the inside of the cavity with phosphoric acid and then prime and seal with PPG's top of the line DP epoxy. The tech sheet says phosphoric acid treatment can promote adhesion, but anything else under the primer could be counter productive. I'm debating whether to spray Raptor inside the cavity before closing it up.

[Bartlett 914]

Thanks all. I'm liking those liners. I think those would be a very good idea here.

I share everyone's aversion to the foam, but in this particular cavity, I cannot say the factory was wrong. I don't know how many have poked around in that spot, but this area forms narrow cavities that extend back about 8 inches to the rear corners of the car. You might be able to get away with leaving them open in a mild climate driving only on paved roads, but in my situation, I can guarantee they will soon fill with dirt and crud to form a moisture trap way worse than the foam with seam sealer ever presented. I live 3 miles down a dirt road so every trip will include a minimum of 6 miles of dust swirling around under the fenders and settling into those cavities where it would be difficult to impossible to clean out. I think the fender liners will help reduce, but not eliminate that. And if the swirling dust isn't enough, the cavities are the perfect size for mason bees and wasps to pack with mud tubes for their nests. I'm convinced that not closing that cavity would be a mistake.

My question is more about what is the best way to close the cavity than about whether to close it. The next question is how best to close it. The factory filled the cavity with foam to provide a backing for seam sealer which was applied over the foam. This worked fine until the sealer dried out, shrank, and cracked to let moisture in where it got trapped by the foam. This was one of the few areas that wasn't rusted on my car, so it worked for 40 years. I've gotta believe that sealer, and maybe foam has improved over the years since these cars were built.

Right now, I can think of a couple ways to close the cavity. One is to just replicate what the factory did with modern foam and sealer. Then add inspecting the sealer in that area to my annual maintenance schedule. The other is to cut a plastic disc to block off the opening and form a backer for applying sealer, then drill a small weep hole after the sealer has cured. That would leave the cavity hollow inside but prevent crap from getting inside. I'm kinda liking this second option but need to think about it more.

Before closing, I will treat the inside of the cavity with phosphoric acid and then prime and seal with PPG's top of the line DP epoxy. The tech sheet says phosphoric acid treatment can promote adhesion, but anything else under the primer could be counter productive. I'm debating whether to spray Raptor inside the cavity before closing it up.

Brent.

My car had them for more than 10 years and I only had liners. I really drove my car a lot. Cross country etc. When we cut up the car it was still perfect. I have the quarters upstairs and I can show pictures if interested. The liners do stop the crap and Bees will not nest there