Back Flushing-Heater Core

(Part 1 Of 2):

(Part 2 Of 2):

Back-flushing the front and rear heater cores must be a separate procedure to get the required flow which is opposite to normal heater operation.

The front and rear heater cores are fed by the same main inlet and return heater water hoses. Therefore, both heater cores can be flushed with one backflush procedure.

1. Turn the ignition switch ON.
2. Set the front temperature control knob and the rear temperature control knob in the full WARM position.
3. Set both fans in any speed and any mode except OFF.
4. Turn the ignition switch OFF.
5. Drain the cooling system.
6. Disconnect the main inlet heater water hose at the inlet heater hot water tube to prevent the backflush material from entering the cylinder block. Allow the inlet heater water (drain) hose to drain into an appropriate container.
7. Disconnect the main return heater water hose at the return heater hot water tube.
8. Install and clamp a garden hose female end fitting into the main return heater water hose.
9. Connect a garden hose to the end fitting on the main return heater water hose and flush the front and rear heater core circuits until the drain water runs clean from the main inlet heater water hose opening.
10. Pulse the flow to loosen any blockage by turning the water on and off several times. Allow full flow for approximately five minutes.
11. Shut off the flushing water supply and remove the adapters, caps, and plugs installed for the flushing operation. Connect all cooling system connections.
12. Fill cooling system with 50/50 mixture of water and Premium Cooling System Fluid E2FZ-19549-AA meeting Ford specification ESE-M97B44-A or equivalent.
13. With the cooling system warm and pressurized, inspect all system connections for leaks and tighten as necessary.