Cooling sensor and radiator fluid leak

I have a 97 saturn SL2, The cooling fan does not come on at high temps. Cooling sensor has been replaced and still no go. The fan is good it comes on with the AC. Also over night radiator fluid is all over. Whats up?
I replaced the thermostat too.

Have you replaced the wire lead to the sensor, and was the correct sensor replaced. there are two of them, one with a grey end and one with a tan end. the one with the tan end is for the fans. The wire leads tend to corrode, so it may be possible you need to replace it

repair the coolant leak, the system can not build pressure if it is not sealed. the cooling fan kicks on at 222F, an unpressurized system can only reach about 212F.

repair the coolant leak, the system can not build pressure if it is not sealed. the cooling fan kicks on at 222F, an unpressurized system can only reach about 212F.
How would I find the coolant leak. It leaks at different times , ussually when I am not around to locate it. Is there a hose at the bottom or hidden some where? All top hoses are ok and when the engine is running , no leaks,, Very strange

Have you replaced the wire lead to the sensor, and was the correct sensor replaced. there are two of them, one with a grey end and one with a tan end. the one with the tan end is for the fans. The wire leads tend to corrode, so it may be possible you need to replace it
The sensor that was supposedly replaced by a mechanic has a silver metal end, I think he replaced the wrong one. I went and bought another sensor and this one has a tan plastic sensor end. This sensor will be located on the drivers side and screws toward the passenger side right? How do I get the plastic lip of so I can get it out. Thanks for the help.

ok woah. the coolant temperature sensor screws into the side of the head just above transmission and below egr valve practically in the center of the head. a new sensor should have a brass tip, the old style was plastic which caused problems. when you remove the sensor from the head it is going to gush coolant so you better have the sensor waiting with teflon tape on the threads ready to go in. also most guys replace the connection to the sensor since it typically corrodes up inside, so a pigtail is also bought but for me mine was good so i didnt need one. as of the coolant loss, it could be so many things. it could be a leaking water pump which means its bad, a pressure leak only caused when pressure is put on the system, hose leak, crack somewhere, leaking heater core(normally noted by a coolant smell inside the car and sometimes puts moisture on windshield with defroster). i mean there are so many things it could be leaking from.

ok woah. the coolant temperature sensor screws into the side of the head just above transmission and below egr valve practically in the center of the head. a new sensor should have a brass tip, the old style was plastic which caused problems. when you remove the sensor from the head it is going to gush coolant so you better have the sensor waiting with teflon tape on the threads ready to go in. also most guys replace the connection to the sensor since it typically corrodes up inside, so a pigtail is also bought but for me mine was good so i didnt need one. as of the coolant loss, it could be so many things. it could be a leaking water pump which means its bad, a pressure leak only caused when pressure is put on the system, hose leak, crack somewhere, leaking heater core(normally noted by a coolant smell inside the car and sometimes puts moisture on windshield with defroster). i mean there are so many things it could be leaking from.
Alright, Thanks for the info, The sensor I bought for replacment has a plastic front..I will return it.This sensor if working correctly should kick the fan on. the fan works only when the ac is on. so the fan is good.
The leaks don't occur untill the car has been sitting a while. No leaks are noticeable when the car is running.
I've even let it run for a while and still no leaks. Very strange. In the morning at times there is fluid leakage under the frt of the passenger door underneath.

well then that could note that the heater core is leaking. there is a hole in the firewall for excess moisture to leak out of the blower box. this is mainly for like a/c and water that comes in through the outside vent. it is a helpful thing too when a heater core leaks so the coolant wont pool in your car. and yes the sensor should allow the fan to kick on at the range of 220 degrees, just at like the 3/4 mark on your gauge. if there is a problem with it not kicking on and relays and fuses are good, then the sensor should be replaced along with the connection so it isnt to foul up the new sensor.