Ford Repair: ?Heater core leaking, engine coolant, shop tomorrow

Question
2003 Expedition with rear A/C & Heating – Leaking - yesterday I noticed engine coolant coming from the drain whole on the rear A/C & Heating unit. The aluminum supply and return lines under the vehicle look OK, so I suspect the engine coolant is from the rear heater core, valve or a fitting leaking. It’s going into the shop tomorrow morning for repair. Is this a common problem with rear A/C & Heating on Expeditions?

Answer
I cannot say that is a commoen problem on Expeditions as I don't have much experience with them.  However, it's good that you're taking care of it as it cause multiple problems for such leak.  One of which, erosion of aluminum tubs, causing A/C malfunction.