coolant leaking - 10v MC2

[hayes myers]

Well..after my timing belt (200 10v mc2) i noticed a leak of my coolant.
(silly warning lamps).  Yep...it was losing coolant.  I had changed temp
sensor (the top side one,front of engine,drivers side, single post for one
wire attachment) and seems there is coolant leaking from there.  Anyone else
have this problem? How tight should this be put on? Is sealant required? I
have 3 or 4 more of the sensors (so cheap at 4bux each)...so i could try
another one. Wondering if i should just tighten up more and see?  I seem to
lose 250ml of coolant in about 250km.... can so much leak here? I see
bubbling/puddling of coolant around the sensor base. Silly question i guess,
but don't want to retorque and mess something up with my enthusiastic
wrenches.
Thanks, Hayes