Just ran into this corrosion issue. Ford has flushed the system, at ther cost, but still no heat. My service rep wants to replace the heater core now but Ford is telling them the heater core is not covered. I am the second owner of this vehicle, 2008 Edge, so I did not receive a letter on the extended warranty. Can someone tell me the specifics on what is covered on this extended warranty or maybe even provide a copy? Would be much appreciated