How to check if a thermostat is good in a 2007 Jeep Gd Ch Lar. 3.7 L And How

to get the air out of the system? Water pump was recently changed, I ran the vehicle for a while & it blows cold air. The upper radiator hose is HOT but the bottom hose remains cool enough to touch. Is the thermostat bad??? How can you tell? Could a bad thermostat cause the bearings to go in the water pump? Or is there still air in the system? I raised the engine rpm to 2.5 & watched bubbles rise out of the filler neck even drove it around 3 blocks & it went up to 239* About 3/4 towards Hot. We stopped, loosened the cap, & refilled it & the temp stayed at 239* & drove it around 3 blocks to get back.
I saw a 5/16 Allen? wrench screw at the end of where the upper radiator hose goes into the engine. Is that to bleed the air out?