I am not the OP of this thread, but a quick update on the subject based on what I recently learned.
Yesterday I was at my Jeep dealer for an oil change and I asked about what would be the normal operating temperature range of the cooling system. According to the service manager, the cooling system only has two "permanent" set points, the low set point is about at ~194F (90C) and high set point is at ~235F (112C). Basically the cooling system would completely turn off (thermostat fully closed and fan @ min speed) if the coolant temperature is below 192F and the cooling system will be completely on (thermostat fully open and fan @ 100%). Anything between these two values is normal, as the system can dynamical move set point for the coolant temperature. As the thermostat and the radiator fan on these cars is 100% electronic and controlled by the ECM, the computer maintains the engine cooling temperature based on the environmental conditions, engine load, fuel economy, speed and etc.
As an example, if the engine is under heavy load, the ECM can maintain the coolant temperature @ 110C, since a hotter engine is more efficient (or basically uses less fuel and generates less heat) . If needed, it could cool the coolant down to 92C, but chooses to maintain it at 110C due to improved fuel economy, reduced engine load and less stress on cooling system. This is especially true for hot weather, as the computer tries to avoid stressing the cooling system for marginally better cooling at hot weather. to According to him, as a general rule of thump, if the engine is generating more heat (conditions like towing, high grade climbing, stop and go traffic, etc) the system will set a higher temperature set point. The set point is also higher at warmer weather. If the engine is not generating extra heat, or if the ambient temperature is low, the coolant temperature is maintained at a lower value (since it could be done with minimal effort). So put it simply, if the coolant is easy to cool down, under given driving conditions, it will cool it down until the lower set point with minimum effort. If not, computer will set the coolant temperature that would be easiest to maintain with minimal load on the cooling system and it would only stress the cooling system if the temperature raises against the upper limit around ~235F. This to some extend also comes down to fuel economy, as running the cooling system consumes fuel and reduce fuel economy. I assume there also is an even higher coolant temperature value that the A/C is tuned off and an alarm is shown (per the manual), this value might be in ~250F, per the given range.
I was actually able to see the system at work to some extend. I my case, the cooling fat is at idle until the coolant temperature hits 230F. At that point, the cooling fan turns on and cools the coolant down back to ~220F and than slows down. However, if you put the A/C on max, it manually sets the radiator fan to 100% (like in any other car), in that case the coolant temperature drops until ~194F, at which point thermostat is closed and further cooling is prevented.
Last edited by Tripod; 07-21-2019 at 09:14 PM.