thermostat bolt

[osaltyone]

So I bought this temp sensor to control my fans, I thought it went in the port on the top of the waterpump, but after researching a bit more I guess it goes on the side of the head, now I got to move it.
When I went to remove the bolt in the hole on the side of the head it I grabbed my 3/8" ratchet and extension, but it doe not to fit. I know this is a dumb question, but do I need a specific tool for this? I have all the torx sockets and they did not fit either. I have been looking @ auto stores @ their selection of tools and don't see anything that will fit. I don't want to run on a switch, kinda like automatic so I don't forget...