Leaking Heater Box Disassembly

This is an interesting topic. I had never heard of this problem. I guess I am lucky mine hasn't started leaking yet. I had contemplated pulling the whole heater box and just putting a plate on the firewall.

Thank you to all the forum posters who contribute to making my love of these cars that much easier to enjoy. After removing my carpet to find some unexpected floor pan issues I was luckily enough to get caught in the rain on my way home from the repairing of my floor boards. This made it very easy to locate my leak(s) just tracing the path from the puddle on my passenger floor board, up to behind my glovebox... Quickly enough I found my resolution right here and had a game plan to resolve this issue.

So off came the inner fender, pulled heater box from firewall, removed ac & heater core from box(able to safely move out of way while still hooked up), removed my heater box, went down to the local Tony's Auto and picked up some Black RTV sealant and a box of 3M 1' Strip Calk. To make sure I don't end up having to remove it again sooner than later I ended up disassembling the whole heater box and resealed it with 3M strip calk, then used the RTV for resealing the heater box gasket to the box and a combo of the RTV and 3M Strip Calk to seal it back to the firewall.

I appreciate all the great info that can be found here and is shared in our B Body community. Thank you again to all who take their time to post! You've all made my life much easier taking care of my Irene.

Here's mine! I had been putting this job off for years... Has anybody else found (or made) a replacement gasket for the box? The original looks reusable, but I wonder if there's something better. BTW, I found a source for the unique M6.2 SEMS screws that secure the box to the firewall, if anybody wants fresh ones.