I used one on that same fitting. It split my thermostst housing.. $400 of welding later it was mostly fixed. I still had to retap the threads and use copious thread sealer on the new fitting.
I would recommend welding in a socket or slitting the fitting with a blade. Almost any pipe wrench, vice grip, or channel lock will cause immense suffering.
Once mine cracked, I wound up splitting the fitting with a chisel and finishing with a saw blade, then using a punch to fold the remnants inward to remove them. Then it was off to the local weldery to get bent over.
