My dau's 1998 Jeep Wrangler with 120k, 4 cyl. 2.5L engine and manual trans is having a whitish smoke or vapor come out of the vents at the bottom of the windshield. She says it smells 'hot' but leaves a film on the inside of the windshield=w/s. No coolant on the passenger side of the floor. She has had to add some coolant to the reservoir, but she has had to do that for some time. She says this happens most notably on cold mornings. I have noticed that the coolant in the reservoir gets black and has an exhaust smell to me. Any ideas on what would cause the white smoke on cold start up? TIA.