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This procedure was taken from a Ford Service Manual for a 4.6/3.8 in 94, so it should work for MOST of you guys. I don't know about the 5.0 HO guys.


  1. With the engine off and sufficiently cool, remove the pressure relief cap, open radiator drain cock and remove the cylinder drain plug (if equipped) and allow coolant to drain.
  2. Close radiator drain cock (hand tighten).
  3. Check all hose clamps for proper tightness and location.
  4. Place heater temperature selector in maximum heat position.
  5. Remove vent plug on water bypass elbow (located on intake manifold behind water outlet connection) on 3.8L engines (at this step, you may want to backflush the radiator, motor and heater core -- steps are below).
  6. Fill engine cooling system with 50/50 mix of antifreeze solution and water.
  7. Leave pressure relief cap off and run engine until water thermostat opens.
  8. Stop engine and add 50/50 mix of antifreeze and water to adjust coolant level as necessary.
  9. Add coolant mixture to the full hot mark.
  10. Install pressure relief cap.
  11. On 3.8L engines, install cooling system vent plug. Tighten to 8-11 ft/lbs.

Cooling System Backflushing

  1. With the radiator upside down, position a high pressure water hose in the bottom hose location and backflush.
  2. Remove water outlet connection and water thermostat.
  3. Position high pressure hose into engine through thermostat housing and backflush.
Note: A pulsing motion will loosen more sediment than a constant flow. Also, if this action does not remove all foreign material, you might need to use a chemical to do the job in conjunction with a pressure flushing system.

Heater Core Backflushing
This should be done at the same time as a cooling system drain and fill.

  1. Disconnect the heater core outlet connection and install a female garden hose end fitting adapter in the end of the outlet hearter hose. Secure with hose clamp.
  2. Connect the female garden hose end of the outlet heater hose to the male end of a water supply garden hose.
  3. Disconnect the heater core inlet heater hose and allow to drain into a suitable container.
  4. Turn the water supply valve on and off several times so that the surge action will help to dislodge large stubborn particles from the heater tubes. Allow water pressure to flow for approximately 5 minutes.
  5. Remove all the hoses and reconnect everything.
  6. Fill the system with specified amount of coolant and all... or resume from above.
It is critical that you carefully follow Ford's procedures for draining and refiling the cooling system or the air pockets may occur.

Ford engines are susceptible to getting air bubbles or super heated air pockets in the cooling system. When these super heated air pockets occur they can exert tremendous stresses on the heads, headbolts and gaskets both physically and thermally and can cause damage to the gaskets. These super heated air pockets don't always
show up as a reading on your temperature gauge.

Some people have different opinions on the radiator flushing and its relationship to head gasket failure. Technicians say that mild cleaners (no neutralizer types) are perfectly okay to use - like Prestone SuperFlush. A backflush kit with a T fitting is okay also, but don't run the engine while running water through the system with a hose and the T fitting. It can put incorect pressure on the water pump and may also allow air into the system.

Dom, Mager Thom
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