How To Restore Your Mopar's Plenum Box - Ice Age Returns

The gasket was removed with a razor blade and put in a safe place. This will be used as a template for making a new gasket, so don't just scrape it off and throw it away.

After the cores are out, the blower motor can be removed, as well as the gasket for it.

All the vacuum actuators are also removed and set aside. The guys at Classic know where they fit during reassembly just by looking at them because they've done so many. Don't rely on your memory-label them. A Polaroid photograph is also a good idea.

One trick Tim showed us was to scribe a small mark on the canisters to help orient them during reassembly.

There are foam seals on all of the doors on the box, and they also need to be removed with care and labeled as to where they go.

Finally, the service label is cut off and saved. We're going to put it back on, just like we found it. It's not original from the factory, but it is original to the car, and it's a piece of history.

After everything is inspected, it goes into the glass beading cabinet. This is the plenum box, and as we said, it's made of fiberglass. The glass beading leaves it looking white. If you do it yourself, take care to use low pressure. Notice that the factory numbers painted on the box (circled) are still there. Classic Auto Air masks off any factory markings before bead blasting to insure they aren't obliterated and lost forever.

Then it's time to visually inspect the parts. This heater core showed a small build-up of deposits (circled) in a few spots, indicating it may have small leaks. Pressure testing revealed that it did. If Classic Auto Air can't repair your cores, they can re-create them from scratch to be exactly like your originals.

To check the vacuum canisters, simply attach a small piece of rubber air hose to one of the ports, plug the other and suck or blow into the hose-if the arm moves, the canister is good. If yours is bad, Classic can repair or replace them.

This is the blower motor resistor. If the coils are intact, it's good. If they're broken, it needs to be replaced. You can scour the swaps, or call Classic for the replacement.

Next, the plenum box gets a simple coating of rattle can clearcoat. Here you can see that when it's wet, it darkens all of the freshly-blasted fiberglass, making it black again. It stays that way after it's dry, as well. After coating it in clear, it looks as good as the day it was originally assembled!

This sticker was also found on the plenum box, and care was taken to preserve it. It, too, was sealed with clearcoat after being masked off and protected during the bead blasting.