Does this sound like a decent idea? Eventually I will treat and seal the holes more permanently (2 of them ~ 1.5" x 6" each - under drivers seat). I'm thinking of using sheet aluminum, silicone caulk and sheet metal screws.

Thanks for your help,
Tom
'86 245 DL 245,000 miles

Don't use aluminum sheet or aluminum rivets.
Use a piece of galvanised steel, steel rivets, and some tar.
You might as well clean up all the lacey, rusted metal around the holes too. Just trim it back with some tin snips. Probably a good idea to squirt some rust proofing oil up in there too.

.

I'm not sure what to say about the spray foam idea... However I would strongly suggest using steel rather than aluminum for patches, especially if you live anywhere the roads are salted in the winter. It'll just turn into white powder in a matter of a few months, unless it's anodised or very thoroughly sealed. Though steel rusts it'll actually last a lot longer than bare aluminum sheet. And perhaps using body seam sealer would work better than silicone, it's cheap too. Available at any body shop supplier and most auto parts shops.
--
Chris, Dartmouth NS Canada 70 M-B 280SE, 83 245DL, 84 244 turbo, 90 780 turbo, 92 VW Golf, 90 740 Rex/Regina

I've used polyurethane foam to fill a rusted seam from wheelwell to trunk (ahem, on a Honda). I then covered it with spray on tar.

It should work OK as a temp fix.

If you are getting holes in your floorboards, how's the rest of the body and structural and suspension components?
--
Norm Cook; Vancouver BC; 1989 745T 210,000KM

the previous owner of my '86 did this already, it seems to fill the hole just fine....but would it maybe hold in moisture? i was somewhat critical of the job but maybe it works? hmff....
has anyone just used rivets and silicone sealer when putting new floor sheet metal in? i dont have a welder...no friends have one either and i need to get this floor fixed. i've found a 240 in the boneyard with good floor pans that i may cut out and rivet in then do some zinc primer and then the undercoat stuff... sound good?

Wow, I like the floorboards and rivets much better than the expanding foam, that stuff'll soak up water like a sponge, causing rust around the foam chunk and eventually your floor falling out. I have a Scout - trust me, it sucks when that happens! If the holes are small, there's nothing wrong with fiberglass cloth and resin. Tape a section of cardboard under the floor to keep the glass from sagging, and you'll be good to go. Remember though, resin has a short shelf life and the stuff at Walmart or an autoparts store will peel and lift - stop by an automotive paint store, they should have fresh. :)

Sarah
R2 1987 245 158k

This subject came up from time to time in Volvo school and their official take on it was that it would retain moisture and cause things to rust out so they would not endorce it. If you do it go easy on it, I have seen that stuff expand a little too far and cause problems where things bulged out from the stuff expanding too much.

Mark