I have an 07 case 430 skid steer. I’m having an issue with the coolant not getting hot enough for the thermostat to open and flow properly kinda new to this not sure what to look for I did buy a new oem thermostat and replace it cause I thought it was stuck open that’s not the case.
Thermostat would have been my first thought, but since you changed it, I would be checking the temp gauge and sender. If you have access to a infrared temp gun, you would be able to check hoses for real time temp, pre thermostat and post, also check heater hoses going in and out.