A friends mk4 golf 1.6 16v 2001 (used to have this car myself, before
I moved to the dark side of diesels)

Anyway I did a vag come scan for him last night as he had a MIL light
on and it saying the "coolant temp sensor" has an error. I cleared the
fault for him it has not come back on but he has all the symptoms of a
failed sensor, fluctuating temp needle etc, poor start from hot and
cold, bouncing rev counter etc. (not sure if that last one is related,
could be a dirty throttle body or a vac leak)

Anyway for the life and light of me I could not find this sensor ?

Does anyone have a breakdown of pictures that shows it location ?

The haynes manual is less than helpful on this one, which was my first
port of call.

I want to confirm its the green sensor as there are blue black spade
fitting ones, so a quick check on location and type is in order before
I order the wrong part. When I did mine VW sold me the wrong part even
though I gave them the car details.

Any help appreciated.