first i'd like to say hi as im new to your site, looks great and will probily be on here a bit.
I'm searching for this invisable sensor too, Its for an 1800 black top zetec 1998. its not between plugs 2 and 3 in the cam cover and not in the stat housing. it's been on diagnostic maching and it found a fault with the 'engine management cooling temp switch'. any ideas? it's not under the cam cover is it? many thanks.