Gang,
For a few months I've been getting a slight exhaust smell when I run A/C in my '66 Starfire. When I restored the car 20 years ago, I trusted 33 year old factory seals to work as new, which was o.k. 50 years on, it's time to reseal and get back to what the engineers intended.

There is a minor exhaust leak, but I'm focusing here on leaky A/C ducts to keep exhaust gases from asphyxiating me & my passengers.

Here's the CSM diagram with my edits in a different font in case they help:

65-66 Big car A/C ducts & seals. Eventually they get old and leak. In and out...

I began by removing the fan motor, with 6 x 1/4 hex head screws. Once out, I shot the electric motor with compressed air to get out 50 year's worth of dust & crap. I hope it helped. It didn't hurt anything.

With the fan out, I had access to the blower assembly. It is both the fan and a plastic/composite intake duct. You can remove the duct using a 7/16 nutdriver & patience. It's plastic, not strong, so don't crack it. Also be careful of all the vacuum hoses, wires and heater core hoses when you remove it. I fear heater core hoses since they often crack the core and you get the glycol bath...

Once the firewall plastic piece is out, the other 2 ducts should more or less slip free once you've removed any vacuum & electric components screwed into them. Like the resistor. Or the heater core clamp. Etc.

My goal was to replace aging seals which seem to be letting exhaust gases into the cabin. Any leaks are probably letting conditioned air out too.

I've noted 3 of 4 seals above to be remade. I forgot the 4th one. It sits between the metal fan and the firewall housing. Mine was good enough to use as a template to cut a new one from closed cell foam.

For new seals, I used a combination of EPDM rubber & closed cell foam. I figure as long as the seal doesn't retain water, it shouldn't harm the carl. 3/16"s thickness X 3/4" width seems about right for the edge seals (#2 and #3 above). I cut the fan/firewall seal from a piece of closed cell foam, then glued it in place with 3M spray adhsive before securing the fan back to its intake duct. The gray foam seal didn't look right so I covered it with black 3M dum dum as a cosmetic fix.

Once everything on the way to the A/C evaporator was removed, I sanded & resprayed metal parts with Krylon satin black to match my engine brackets. With the plastic/composite parts, I just scraped off the old seals & sealant (dum-dum) and cut new EPDM gaskets from 3/16's X 3/4" adhesive tape. U channel EPDM would have been better, but I cut what I had on hand to fit. It worked better than the worn out seals from 1966.

The new 3/16's thick seals made for a tight fit on reassembly, but a short fight gives me confidence in long term performance. For anyone following along, I just added a fake OAI to this car so I'm apparently in duct mode.

While the plastics & metal ducts were out, I cleaned all of them inside & out with dish soap, then sanded and resprayed the metal pieces. The composite pieces got a bath in Klasse vinyl protectant which gave them a nice shine & clean look. Klasse is good stuff.

My final step was to clean out the dirt in the evaporator cavity. My evaporator works fine, but the plastic box in front was 10% full of dust, leaves, and crap. I took 3 steps to clean: 1) shop vac loose stuff; 2) scrape the stuff deep on the drivers side lower corner free for more vacuuming; 3) blow compressed air into the evaporator cavity to get anything that's left. It ain't perfect, but it's better.

I got it all buttoned up just before my family got home.

Here's what it looks like:

'66 A/C assembly, resprayed with Krylon satin black, new 3/16's seals between the ducts and Klasse vinyl protectant to make plastics look good.

I didn't know the factory also gasketed the resistor module. I guess I have some more gasket making to do.

Suggestions, improvements, or comments welcome. It took probably 4 hours start to finish. Fun afternoon.

Chris

PS: I took it for a short test drive. Exhaust smell is gone & air volume from the climate control system is clearly higher than before. Cool!