Leaking at the housing were the theamostat

My car is leaking water from my thermostat area. I took
one of the horses off from the motor were the heater hose
goes. Bottom hose. The top hose going into the engine the
metal piece were the horses connect was rotting. My buddy
wants to take the whole pipe off. I think it's running along
side of the block to the water pump. It's cast alluminam.