I believe thats what it is. Its located next to the overflow tank. It is the last part of the cooling system before it goes into the top of the motor. My hose on top of my engine was leaking and i tried pulling the hose out and snapped the other end off. I cannot for the life of me find this part or what its called. Does anyone know anything about this part or where i can find a replacement. It may be a standard GM part. Thank you if you can help. I have attached a photo.