I keep refilling the coolant but its not leaking out from under the car. So I have no idea where its going.
Not an SHO. the other problem is when it overheat the inside of the car fills up with coolant fumes. It obviously has a leak but its not leaking under the car.
Which engine? Vulcan or Duratec? You might have a leak from the timing chain gasket, and coolant drips onto the exhaust pipe, which instantly vaporizes, and is sucked into the HVAC system at the base of the windshield.
