Here is the owners manual for my car: http://www.fordservicecontent.com/Ford_Content/Catalog/owner... On page 259, under the heading "Fail-Safe Cooling".

  If the engine reaches a preset
  over-temperature condition, the engine
  automatically switches to alternating
  cylinder operation. Each disabled cylinder
  acts as an air pump and cools the engine.
  When this occurs, your vehicle still
  operates, however:
  • Engine power is limited.
  • The air conditioning system turns off.
  Continued operation increases the engine
  temperature, causing the engine to
  completely shut down. Your steering and
  braking effort increases in this situation.