How to remove thermostat housing case?

I am having trouble removing the thermostat housing. So to be specific, I am not talking about the thermostat cover, neither the thermostat itself. I am talking about the actual housing in which the thermostat sits in. that case has a coolant relief valve/screw to remove any air in the cooling system. Now I removed the two bolts that hold the case. There is a pipe attached to the case, that's where I am stuck. How do I remove that? do I pry it off? does it screw off? I tried both, I really dont want it to break because it was a hassle just finding that case. Any help or videos or would accepted and appreciated. Thanks in advanced.