As TX said, a pressure tester will help in finding the leak......those little heater hoses under the dist seem to like to leak, usually because the o-ring at the base of the dist will go bad and allow oil to leak onto the hose causing it to become weak

 

Yeah, that one already got me when I got the AC working, it blew that hose. Which was also nice in that it fixed my oil leak! lol

 

So if it is the heater core, it would only leak with temp set to hot, yes?
I've never pressure tested a cooling system before; should I have the heat valve open, do I need to do anything with the t'stat?

 

No, heater flow valve only isolates flow to the heater core. Pressure will equalize across the valve from return side. Thermostat has a small bypass that allows pressure to equalize w/ a closed thermostat.

Pressure tester is available for loan from AZ, etc. Be sure they have adapter for your radiator.

good luck

 

Well, when I had gone out to check, the system and reservoir were still full, so I put it off and it's been fine up until yesterday, and yes, I had been slacking off on checking since it was good for a week.
I'm guessing it is the heater core, having the heat on yesterday morning was supplying plenty of AF odor. My thinking is if I'm not seeing any sure signs, wet carpet, windshield residue, I may not see anything pressure testing. So for now, being the weathers dipping at night i'm going to drain and refill with mix instead of just water and bypass the hater core for the time being.

 

Check heater core connections on outside of firewall. Sometimes they can leak into pax compartment.

good luck