[bleepster]

I have the same car - i had the same problem.

Not to burst your bubble but prepare for the worse.
Mine ended up being the lower intake gasket. about an $800 repair (at a shop) Do as described above, and keep your eye on your anti-freeze.

Also - look at the passanger side of the engine - where the intake meets the head. usually you can see "wet marks" where the head meets the intake. if you see evidence of that, i recomend getting a pressure test done to verify any leaks.

I have had to have my lower intake done twice. (once under warranty, 2nd time at my expense).

about 1 month ago I had the unfortunate expense of a head gasket leak. $1100. But that included hot tanking the heads and resurfacing.

Car runs like a champ now. I love my Lumina, and I will hold on to it until it totally blows up.

1997 Lumina, 3.1, 128,000 miles

and yes - sensor is on radiator - about 3" below the filler neck