Part name/location/troubleshooting

Hi, I own a 1995 Saturn sl2 DOHC. About 2 years ago, I started having some cooling system issues; overheating mainly. So I decided to begin my descent into understanding how my car mechanically operates! I bought the car repair manual and began studying. I started to change Solenoids, sensors, valves, hoses, water pump, thermastat/&housing, etc. I did a good jod and my car ran and still runs great. A couple weeks ago my car started loosing coolant. I inspected the cooling system and found out; after a cooling system pressure test also, that my reservoir had a small crack in the bottom, and the 90 degree hose from reservoir to stainless heater line needed changing along with themolded heater hose that attatches to the same stainless heater line. From there the molded heater hose runs below the thermastat housing and fits onto a nipple that is connected to a nut. What is the connection called? And since I have changed that hose, I have had coolant leaking from around the threads of that piece. I tried tightening it and it seemed to help. But still leaks a little and intermittently. Especially if I don't run the heater and the car gets to normal operating temperature and then when I park and turn it off, it will leak a little. What is that connection called? Can I change it? Someone said it was a heater inlet fitting and someone else said its called a bleeder valve. Which are two different parts all together. Would yo help me please? Thank you- Jason