It probably just needs a new o-ring. Disconnect the wiring connection and undo the bolt holding it in and it should come out pretty easily (rotate it back and forth a little while pulling). Remove the o-ring(s) and take them to an auto parts store and have them size it up to a new one. Or if you can find an engine diagram and locate what that particular sensor is you should be able to get the exact OEM part. Either way it should be a cheap and easy fix, or at least an easy way to find out that was not what was leaking
