4RINGSx3

I am in the process of replacing my blower motor (put up with the squealing long enough) & heater core (while everything is removed/opened up) on my '95.5 S6 (141K miles). Following the April 2013 C4 Heater Core Replacement tutorial authored by Dave F ...THANKS Dave! Have the A/C & Heater Blower Motor & Fan Housing removed from the car and separated into it's 2 halves. Also have on hand the new OEM foam gaskets (purchased from an Audi dealer) for when the reassembled Housing is ready to reinstall but have a couple of questions regarding these gaskets....

1. Have the sticky backed foam gasket (Part #431-819-225, 54" long) which I understand is the "seal" where the Housing contacts the "firewall" rectangular opening (see photo in referenced DIY, Step #23, red firewall). Noticed the old gasket in this location seems to be impregnated with some type of substance to perhaps enhance it's water sealing characteristics. The new foam gasket is just plain foam...should this gasket be treated with something prior to installation?

2. Also purchased 2 other sticky back foam gaskets which appeared on the dealer's computer diagram (see parts diagram in Step #24 of DIY, parts #9 & 10 in diagram). Part number of these gaskets are: 443-819-229-A (3/4"wide x 3/8"thick x 8-3/4"long) and 443-260-423 (1/2"wide x 3/8"thick x 18-1/4"long). The dealer computer diagram is not very conclusive as to where these gaskets are used. Are one or both of them used where the L & R plastic footwell ductwork connects to the Housing (see footwell photo in DIY at Step #20). If not here then where?

In advance, thanks for the help & guidance.

GoHeels

Think it was some glue substance they used with the foam at the factory, to make it more water tight.

I tossed out the cheap audi foam, since it's not closed cell, and just used ~3/4" weatherstripping from Lowes, which you can't blow through. It comes in a ~10 foot roll for a few bucks and works fine. It snugs up nicely when you tighten things down. Start at the top middle, peel the backing off, and work around back to the top. Get it lined up so it works well around the opening. If your drain holes happen to get clogged it should keep water out of the cabin. Perhaps a month later tighten the strap a bit if needed.

Picture - from inside the car you'll be able to see a bit of the foam squishing in when its tightened down