Checking/removing Heater assembly

I agree; I pulled my heater box when I was painting the engine compartment and found a ton of debris in the area of the heater core. When I pulled the core out to have it rotted out the radiator shop said that it had been leaking for quite some time and was beyond repair. By the way, my heater worked before I pulled the box. Be very careful pulling off the clips the plastic box is easily damaged.