DB, I do not think this is really a huge mystery. If there is no water to transfer the heat, the sensor will read the "ambient" temperature in the vicinity of the sensor. The outlet of the coolant of the engine may be significantly cooler if there is no coolant to transfer the heat from the cooling jackets, even if the cooling jackets are very hot. D^2 At 01:39 PM 8/21/2002 -0700, you wrote: >OK, thanks for the update. I'll file away your mystery temp sender reaction >in my "look into it some day" file!