Sounds like a heater core went south on you. Hoses will leak to the outside of the car.
I doubt that your coolant mixture broke the core. However, fill only with 50% water and 50% coolant as this is the most efficient mixture. Water is what actually cools the engine. Coolant keeps the water from boiling or freezing.
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ASE Certified. 10 years Diagnosing, Repairing, Maintaining Automobiles