Ok, can anyone with a mustang thats has a cold engine check this for me. On the coolant overflow tank where you screw on the cap... can you check if theres a little square hole on the black plastic part. Heres a picture to explain this better:
Right where the arrow is, but on the mustang overflow tank. Is a hole right there nearest to the engine side.
edit:
Right where the arrow is, but on the mustang overflow tank. Is a hole right there nearest to the engine side.
edit: