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Heater box rebuild question


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Well my heater box rebuild is working out great. Just waiting on the seals where the core inlet and outlet stick through the top. New fan installed and runs smoothly.

My question is what to use as a seal between the top and main box (this is the area that has the 6 rivets) I have 3/8 closed cell I used for the flaps. Is this too thick for the top seal? I dont want to cause too much pressure on the rivet areas and create cracking

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The closed cell foam on the flapper may be too thick. Test the operation before you rivet the whole thing together. I used thinned foam and still needed to chamfer some of the edges.

You know what a job it is to pull the heater and to rebuild it. Take the extra time and try to make it operate perfectly. That said, I still need to finish adjusting the cables on mine that I rebuilt several months ago.

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Strip caulking to seal the whole box to the opening in the firewall.

The closed-cell foam is to seal the flaps inside the heater box. Closed cell foam does not retain moisture nearly as much (if at all) as the old open cell foam did. The old open cell foam on the surfaces of the flaps has usually disintegrated and disappeared into the carpet by now. I used some 1/4 foam that was glued into place on the flaps. On a couple of the edges I had to round them to get a good seal inside the heater box.

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