tell me if its my heater core or not. when im driving everything seems fine untill i step on it or pass another car. then i smell coolant threw my vents. and the plastic near the bottum carpet up front is more oily then what coolant would feel like and it dosnt smell like coolant. so it cant be leaking. any help. ive been stumped for 3 months on this one. and i am loosing coolant but i dont know from where. no leaks underneath the car at all.