Rust proofing rear wheel wells, I have questions Options

[john77]

While I have the arches cut for the flares I figured it was a good time to strip the wheel wells to bare metal, fix anything I find, and reseal them. I’ve completed the fronts, but just started stripping the rears yesterday and have some questions.

What’s the best way to reseal/rustproof the section above the rear light housing?

I’ve stripped a lot of 1970’s German rubberized seam sealer in my time but was surprises to find that section was filled with what looks like some kind of expanding foam. The area is obviously a crud catcher, so I’m wondering the best way to seal it back up? Seam sealer? Or is there some other product I should fill the void where the foam was first?

https://photos.app.goo.gl/2RYXDYXEVmRorirE9

The other section I’m wondering about is in the front of the well where the sail panel meets the quarter panel (the L shaped section coming down into the wheel well).

It seems odd that this was so open - is it supposed to be covered in seam sealer?

I’ve scraped some debris out of it, but would love some advice on what to do with it when I paint/reseal everything.

https://photos.app.goo.gl/K2gqHAMPtzvMgiMB7

[bbrock]

I've been mulling what to do with that area for over a year now as I get my car closer to going back on the road. Here is the problem I have with how people decide if things the factory did was good or bad. We clean off a bunch of undercoating and find rust underneath and condemn the undercoating as a moisture trap that promotes rust rather than prevents it. Same goes for the body foam shot into the tail light section and sail panels. We pull nearly 50 year old foam out and find rust and immediately blame the foam. What we rarely consider, and almost never have data to evaluate, is how quickly those areas would have rusted WITHOUT those products being applied. These products have a service life and it is not surprising that they become ineffective or even counter productive when they begin to fail. Since we can't answer that question, we can only guess about the right choice.

Here are a couple things to consider though. My car had the same rusted out sail panels that we see on so many others. The rust was in the exact same places. When I removed them, there was zero evidence they had been replaced before. Perfect factory spot welds were intact and absolutely no hint these were not original. Yet, when I removed them, there was NO foam inside. I don't know why, but there wasn't. Yet, they had rusted the same as so many others. It's only one sample, but worth thinking about. Also, AFAIK, all modern car manufacturers still apply body foam and undercoatings at extra expense. Why? Modern materials may be better than the old stuff, but again, worth thinking about.

For my own car, I'm strongly leaning toward replacing the foam and seam sealer in the tail light section. The reason is that every trip in my car will include 6 miles of gravel road. Even at low speed, dust is likely to settle and accumulate in that little hollow. I doubt wheel well liners would seal well enough to prevent dust buildup but foam and seam sealer will. I'll treat it as a maintenance area and inspect every year to make sure the sealer remains intact to seal the cavity. In addition, the entire car has 3 coats of epoxy primer and I will likely spray the cavity with cavity wax before applying foam. I have no idea whether it is the right or wrong decision, but I haven't found suitable information to confidently know what the right decision would be. Simply condemning the foam because it is found in rusted areas is not good enough for me. The factory applied foam to areas the already knew would be rust trouble spots. That's why it was put there to begin with.

[john77]

I have nothing against what the factory did, it seems to have worked very well on my car because all I’m finding is clean metal underneath it. I’m just wondering the best way to replace it now I’ve removed it.

I've been mulling what to do with that area for over a year now as I get my car closer to going back on the road. Here is the problem I have with how people decide if things the factory did was good or bad. We clean off a bunch of undercoating and find rust underneath and condemn the undercoating as a moisture trap that promotes rust rather than prevents it. Same goes for the body foam shot into the tail light section and sail panels. We pull nearly 50 year old foam out and find rust and immediately blame the foam. What we rarely consider, and almost never have data to evaluate, is how quickly those areas would have rusted WITHOUT those products being applied. These products have a service life and it is not surprising that they become ineffective or even counter productive when they begin to fail. Since we can't answer that question, we can only guess about the right choice.

Here are a couple things to consider though. My car had the same rusted out sail panels that we see on so many others. The rust was in the exact same places. When I removed them, there was zero evidence they had been replaced before. Perfect factory spot welds were intact and absolutely no hint these were not original. Yet, when I removed them, there was NO foam inside. I don't know why, but there wasn't. Yet, they had rusted the same as so many others. It's only one sample, but worth thinking about. Also, AFAIK, all modern car manufacturers still apply body foam and undercoatings at extra expense. Why? Modern materials may be better than the old stuff, but again, worth thinking about.

For my own car, I'm strongly leaning toward replacing the foam and seam sealer in the tail light section. The reason is that every trip in my car will include 6 miles of gravel road. Even at low speed, dust is likely to settle and accumulate in that little hollow. I doubt wheel well liners would seal well enough to prevent dust buildup but foam and seam sealer will. I'll treat it as a maintenance area and inspect every year to make sure the sealer remains intact to seal the cavity. In addition, the entire car has 3 coats of epoxy primer and I will likely spray the cavity with cavity wax before applying foam. I have no idea whether it is the right or wrong decision, but I haven't found suitable information to confidently know what the right decision would be. Simply condemning the foam because it is found in rusted areas is not good enough for me. The factory applied foam to areas the already knew would be rust trouble spots. That's why it was put there to begin with.

[bbrock]

I have nothing against what the factory did, it seems to have worked very well on my car because all I’m finding is clean metal underneath it. I’m just wondering the best way to replace it now I’ve removed it.

Oh I hear you. I was just reacting to the many frustrating hours I've spent trying to figure this out myself. In fact, there is a thread on here somewhere that I started asking this very question.

As for fender liners - I think they are great and am considering installing them. The concern I have in my situation is that the fine dust kicked up even driving slowly out to pavement might drift past those liners and still accumulate in that cavity. The down side is that the liners would require removal to inspect that area. With or without liners, my leaning is toward filling that cavity and sealing it so dust can't get in there. That may be the bottom line on what is "best." It might depend on the kind of conditions we drive our cars in. If I planned on only driving my car on good roads in fair weather, I wouldn't be nearly as concerned about leaving that cavity open.

[Jamie]

I have nothing against what the factory did, it seems to have worked very well on my car because all I’m finding is clean metal underneath it. I’m just wondering the best way to replace it now I’ve removed it.

Oh I hear you. I was just reacting to the many frustrating hours I've spent trying to figure this out myself. In fact, there is a thread on here somewhere that I started asking this very question.

As for fender liners - I think they are great and am considering installing them. The concern I have in my situation is that the fine dust kicked up even driving slowly out to pavement might drift past those liners and still accumulate in that cavity. The down side is that the liners would require removal to inspect that area. With or without liners, my leaning is toward filling that cavity and sealing it so dust can't get in there. That may be the bottom line on what is "best." It might depend on the kind of conditions we drive our cars in. If I planned on only driving my car on good roads in fair weather, I wouldn't be nearly as concerned about leaving that cavity open.

If you do decide to replace the foam, what type of foam would you use? (IMG:style_emoticons/default/confused24.gif)

[bbrock]

I have nothing against what the factory did, it seems to have worked very well on my car because all I’m finding is clean metal underneath it. I’m just wondering the best way to replace it now I’ve removed it.

Oh I hear you. I was just reacting to the many frustrating hours I've spent trying to figure this out myself. In fact, there is a thread on here somewhere that I started asking this very question.

As for fender liners - I think they are great and am considering installing them. The concern I have in my situation is that the fine dust kicked up even driving slowly out to pavement might drift past those liners and still accumulate in that cavity. The down side is that the liners would require removal to inspect that area. With or without liners, my leaning is toward filling that cavity and sealing it so dust can't get in there. That may be the bottom line on what is "best." It might depend on the kind of conditions we drive our cars in. If I planned on only driving my car on good roads in fair weather, I wouldn't be nearly as concerned about leaving that cavity open.

If you do decide to replace the foam, what type of foam would you use? (IMG:style_emoticons/default/confused24.gif)

I've been looking at this 3M Flexible Foam Not cheap, but looks like it might be right for the application.

There is also Evercoat Sealant Foam that is a little less expensive but not by much.

But to be honest, I haven't settled on anything yet.