Closed cell expanding foam, For all those nooks and cranys that collect road grime Options

[tbox56]

I have been working on a little bit of rustoration on my 72 subie conversion, and found a couple of areas that have some of the dreaded 'rust bunnies'. One of these is just behind the doors, just on the inside of the vent tube, and the other is by the taillights on toward the outside of the car. after looking at and repairing these areas, i think that the best way to protect them is to keep all of the road grime and moisture out. My thought was to take some 2 part expanding closed cell foam and fill these spots. I found three products on 3M's website that look like they would work. Does anyone have any experience with these products? Foams and NVH

Thanks in advance
Thomas

[tbox56]

I understand that done improperly the foam can act like a sponge, however all of the foam in the car is 38 years old, and seems to have done a pretty good job. On my car i have one corner that still has the factory foam in it, and one that it was removed to replace the fender a number of years ago. The one that was replaced is now full of road grime, sand, pebbles and the like, and beginning to rust, while the factory foam is still rust free and solid.. It would seem to me that done properly, and sealed, i would be miles ahead of a bunch of sand in that corner.

Further thoughts?

[SirAndy]

I understand that done improperly the foam can act like a sponge, however all of the foam in the car is 38 years old, and seems to have done a pretty good job. On my car i have one corner that still has the factory foam in it, and one that it was removed to replace the fender a number of years ago. The one that was replaced is now full of road grime, sand, pebbles and the like, and beginning to rust, while the factory foam is still rust free and solid.. It would seem to me that done properly, and sealed, i would be miles ahead of a bunch of sand in that corner.

Further thoughts?

Yes ...

I have the exact same scenario on my car, but with the opposite results.

One rear fender was replaced at least 15 years ago and no foam was installed. The other side still had the factory foam.

When i did my rust-o-ration, the side *without* foam had no rust what-so-ever in the cavity over the taillights.

The side with the factory foam looked *ok* initially. The foam looked solid and there was some sort of seam sealer around it with undercoating on top.
Once i started digging out the foam, the foam had rust sticking to it! When i was done removing the foam, i found that the area right above the tail light was paper thin with a few pinholes in it. It had rusted from the inside out.

The foam *looked* solid before i removed it, but it wasn't. The other side, without the foam, had the opportunity to dry after it got wet.

Does that area collect dirt? Sure it does. That's what a pressure washer is for. A solid coat of paint and a occasional pressure wash will go a long way to keep the rust away.

I don't think foam is the right answer ... (IMG:style_emoticons/default/shades.gif)