I seem to remember using an extension with the socket on the end, between the heater hoses. Can't remember if there was a bracket holding the hoses to the firewall, if so, I'm sure I loosened, or removed them to get more movement to get hoses where I needed them. Then take the long extension between hoses, attach Allen socket, and remove bolt. Doing this gets the actual socket wrench up away from the hoses for turning action, instead of down there in the tight spaces.