Hi Susan,

Did you ever find/fix the source of the water coming through the "accordian thingy"?
A friend of mine was a pro bodyshop man. He said that he also heard that silicone was supposed to corrode metal, but that he never personally saw any evidence of such and used it himself. I know that uncured silicone gives off acidic fumes, so maybe it causes problems when it's not allowed to dry thoroughly, (under carpets, painted over too soon, etc.)
It's also incredibly tough. If that's the easiest way to fix your leak, I'd say go for it. Is it an empty hole or are wires going through it? If wires are going through, make sure none of them rest against a metal edge; eventually, it'll cut through and ground (short) the circuit. Maybe try to wrap some heavy cloth tape around the wires 1st, then stuff in the silicone.
A stop-gap type of substance: plumbers putty (hardware store). Kind of like play-dough.
--
'84 '285' rice-eater with lotsa hp & performance goodies