You need to follow the instructions in your FSM to get the old heater core
out for inspection. You should be able to see signs of water leakage in
the
housing after you remove the core. If you don't see leakage evidence
there,
take a careful look at everything else hooked to your cooling system,
especially the heater control valve - your leak may be there.
Take the core to your local radiator shop for a pressure test. If it
fails,
let them fix it.
There is an outfit selling heater cores for old MOPARs on eBay - I haven't
dealt with them because they couldn't help on the special core for the ATC
cars, but they did have one for a standard 67 heater, and may have one for
yours too. The price might be better than having yours repaired, or it
might not - you'll have to do the research.
I recently had the core on my project 67 tested, and it failed. Then I
found out that the cars with ATC have a different core, one which is no
longer available without adapting another, much larger core, so the cost
of
rebuilding it was quite high, but it can be done.
Dick Benjamin
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