1998 Ford F150 Owner Guide 1st Printing - Page 168

Maintenance and care Leave a 50/50 mixture of engine coolant and water in your vehicle year-round in non-extreme climates. What you should know about fail-safe cooling (if equipped) If the engine coolant supply is depleted, this feature allows the vehicle to be driven temporarily before incremental component damage is incurred. The "fail safe" distance depends on ambient temperatures, vehicle load and terrain. How fail-safe cooling works If the engine overheats, the engine will automatically switch from eight to alternating four cylinder operation. Each disabled cylinder acts as an air pump and cools the engine. When this occurs, the engine coolant temperature gauge will move into the red area and the light illuminates. The service engine soon light will illuminate, indicating that vehicle service is required. The vehicle will still operate, but will have limited engine power and no air conditioning capability. Continued operation will increase engine temperature and cause the engine to completely shut down. The vehicle will coast to a stop. H C 168