I posted a couple days ago about coolant temp while having a coolant filter installed. Filter is plumbed from therm. neck to filter to degas bottle with temp sensor on filter head.. on a 30 Deg Day running 70 mph gauge reading around 185-190.. now at idle 5-10 min temp drops to around 170-180.. I installed a tee at pump and ball valves at filter head to cut off flow and to still read engine temp however the sensor will not get enough flow of coolant over it to give a accurate reading.. You can actually watch the gauge drop when you cut out the filter..

I removed the coolant filter altogether and installed the temp sensor into the therm stat. housing and my readings while running 55-70 mph gauge reads dead on at 192 deg.. running below 55 gauge reads 185 deg..at Idle 5-10 min I get a reading of 180 deg.. Is this normal for these engines or do I Have something going on.. I dont hear my fan running while driving either,, I know during this past summer my engine temp stayed at 192 deg.. I replaced the thermostat when I changed over to ELC coolant.
I'm going to put coolant filter back in and move the temp sensor to one of the block drain ports and see what kind of readings I get with the filter cut in and cut out.. just trying to figure what the norm is..

 

Sounds normal to me. I have a OEM T-Stat rated at 189*. My temp sensor is mounted in the coolant filter head and I see about 180* running empty. The temps will be a bit cooler there do to being remotely mounted. You have to remember that the t-stat is not an open/close device. It starts to open as the temp is increased and should be full open within a few degrees over the rating. So yours may very well be opening at say 182* and fully open at say 195*. Once it opens the flow of fluid will go through the radiator and begin to cool.

The engine fan will most likely not engage in the winter as it is temperature dependent and you are not getting it warm enough to kick in.