I am into a major rust repair doing the lower edge of the firewall both front toe boards back to the seats and rust out in the front of the rocker up about 6 inches on the door pillar. When cutting out the rusted material, I found two types of sealant so wondering what to use from today's available materials.

First is the lower portion of the front door pillar. In between the inner kick board metal and the outer door pillar sheet metal is a pocket area in front of the inner structure for the door support. It feels like a sponge and to me it appears it could hold water trapped in there. I don't know if it is a sealant or intended to add a little structural support. It only goes up from the bottom about 2 to 3 inches so there is not much there. Wondering what I should use to replace it before closing up the inner and outer sheet metal.

Second is where the rocker meets the front door pillar. on the underside There is a tab from the end of the rocker welded to the bottom of the door pillar sheet metal assembly. There are two gaps, one at the top and one at the bottom inside the front of the rocker. The original had a very hard sealing material to fill up those gaps and keep water out of the inside of the rocker. It looks almost like some kind of expanding foam. The material is similar to what is used filling in gaps where the lower front of the firewall, toe board and inner fender well meet. Wondering what to use to replace this material.

 

GM used seam sealer (tons of it) for most if not all of the butt joints in the unwelded and welded areas. The crap is pliable for a while, then hardens up (eventually cracks and allows water to penetrate).
Since I am in the middle for prepping for paint, I have had to chip out and replace that stuff everywhere it seems. I use ACDelco GM Original Equipment 10-2013 Body Joint and Seam Filler Compound.
It was $11 a tube, but due to inflation it is now $19.20!


I did not (thankfully) have to go into my A pillars; but I do remember a thread about some sort of "sponge" in the very bottom, by the cowl.

 

Yeah, I just don't know why that sponge stuff is in there. Anyway, thanks for the link on the sealer. I will get some on order right away as I am just finishing up cutting and prepping patch panels (big job with the door pillar issues) so want to get it on hand to do the inside seals before welding in the patch panels.