This is the motor part on the photo. Maybe there's only a leak behind the bolt. But to be sure you have to take of the black cover of the sensor part. That's not so difficult, see fore the manual.
If it's only leaking from the hole of the bolt, then i would suggest that you put some liquid gasket in it and put the bolt in again.
See the pictures for more detail. Because the coolant is on the outside of the engine house, there's only a little space between the coolant area and the hole of the bolt.
Greetings from Holland.
Jos Velthoven