Thermostat housing issue???

[ellisjay2]

I flushed my cooling system and pulled the thermostat out, but broke a round cap shaped tube that was screwed into the top of thermostat. Only a section broke off, and the rest is still screwed in. It has some kind of valve needle sticking out of the screwed in piece that looks like to me would rise when thermo opened and then coming out of the round piece that broke were two small ports, pointing towards the carb. I've been trying to find this exact fitting to replace or replace the whole thermo, but the only ones I've found dont have the attachment just solid pieces. I looked on lmc trucking and 32-0160 under thermostat looks to be the exact one. The issue im having now is that when the motor has cooled after running, when I open radiator cap, some coolant comes out under pressure, as if the part were some kind of pressure release valve or something????