I did some searching and could not find threads on this topic...although they're probably out there if I knew the right search terms

So now that it's cold here in Indiana [in the 20s at night], I pay even more attention to coolant temps. I run a two tank WVO system with three sources of heat for the WVO: flat plate heat exchanger, hard lines with coolant wrapped around WVO filter, and coolant lines running back to WVO tank with several coils in the tank to heat the oil back there.

I regularly checked the coolant temps during the summer not only by the gauges but by hand. Usually, all the lines carrying coolant were too hot to touch.

After a 45 minute drive last night, I checked the lines and there were spots that were VERY hot and other spots that were barely warm. The thermostat housing was very hot on one side and only warm on the other, but there were also spots in seemingly random places throughout the lines that were hot or only warm.

So what gives? Thermostat, clogs in the system, ?????