I have a 2001 jeep grand cherokee 4.7L V8 engine. I started it up today. Let it warm up for a couple minutes due to 20 degree weather today. I drove down the highway about 5 miles and I notice a burning smell. I look in my rearview mirror and there was a white cloud of smoke or steam comin from underneath the rear of the vehicle.I had my heater on high the whole time. I pull over and turn off the vehicle right away. I let it cool off for about 5 minutes. Turn off the heater before I turn it back on. I head back 5 miles from where icame from without the heater on. There was still smoke coming from underneath but not as much. I open the hood and there seemed to be some liquid splashage towards the back of the engine. Can u please give me some sort of explanation to this happening which hasn't happened prior? I haven't driven it since due to being afraid of more damage. Thanks.