if you have the valve its back by the firewall where the coolant lines run in thru. i took mine out because it broke.

 

Well the probe that the computer uses plugs into the beginning of the heater hose so I'm assuming there's coolant flow there with the heater off or on.

 

I went to the junk yard and picked up another t-stat housing, then drilled a hole in the bottom to accept the brass fitting that came with the gauge then I used some jb weld to seal around the hole. Then ran the sender wire back through the dash. works great no leaks and you can only see it if you look really hard. I will try to get some pictures up soon. btw mine is a 96 xj