F 350 2WD Pickup V8-460 7.5L VIN G EFI (1997)
Heater Core: Service and Repair
Back Flushing-Heater Core
All engine cooling system flushing and back-flushing procedures must include a separate back-flushing of the heater or air conditioning/heater system
heater core, after the flushing or back-flushing of the engine cooling system. This will prevent engine cooling system particles from clogging the heater
core tubes and reducing (or eliminating) coolant flow through the heater core.
The heater core must be back-flushed separately from the engine cooling system for proper back-flush water flow direction through the heater core.
1. The correct heater core back-flushing procedure is as follows:
Disconnect the outlet heater water hose from the water pump fitting and install a female garden hose-end fitting adapter in the end of the outlet
heater water hose. Secure with a hose clamp.
2. Connect the female garden hose-end of the outlet hose clamp to the male end of a water supply garden hose.
3. Disconnect the heater core inlet hose clamp from the engine block fitting and allow to drain onto suitable container.
4. If a heater water control valve is installed in the heater core inlet hose clamp, check to be certain the heater water control valve is open (no
vacuum).
5. Turn the water supply valve on and off several times so that the surge action will help to dislodge larger stubborn particles from the tubes. Allow
full water pressure to flow for approximately five minutes.
6. If a heater water control valve is installed in the heater core inlet hose clamp, apply vacuum to the water valve vacuum motor to make sure heater
water control valve operates and closes properly to prevent water leakage. Replace the heater water control valve if required.
7. Remove the heater water hose and female garden hose-end adapter from the end of the outlet hose clamp and connect the outlet hose clamp onto
the water pump fitting.
8. Connect the inlet heater hose onto the engine block fitting.
9. Fill the cooling system.
10. Test the system for proper heater performance.