So this is my first tdi. The car is a 2015 it was over heating and not loosing coolant. Found the cooling fan wasn't running changes it. Still got hot not loosing coolant. Then dpf light came on. Changed the thermostat and drove it. It got halfway between normal temp and hot drove for 40 miles like that at 45 in 4th gear to clear dpf. Light hasn't gone off and gets hot normal driving. What should I do now.