Flushing - Heater Core

CAUTION: The heater core must be back-flushed separately from the engine cooling system for proper backflush water flow direction through the heater core.

DESCRIPTION
All engine cooling system flushing and back-flushing procedures must include a separate backflushing of the 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.

PROCEDURES
1. Disconnect the heater core outlet heater hose from the return fitting. Install a female garden hose-end fitting adapter in the end of the outlet heater hose and secure with a hose clamp.
2. Connect the garden hose end of the outlet heater hose to the end of a water supply garden hose.
3. Disconnect the heater core inlet heater hose from the intake manifold fitting. Allow to drain into a suitable container.
4. If a water valve is installed in the heater core inlet heater hose, make sure the water 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 heater core tubes. Allow full water pressure to flow for approximately five minutes.
6. If a water valve is installed in the heater core inlet heater hose, apply vacuum to the water valve vacuum motor. This ensures proper operation of the water valve and proper closure with no water leakage. Replace the water valve if required.
7. Remove the hose clamp and female garden hose-end adapter from the end of the outlet heater hose. Reconnect the outlet heater hose onto the water pump fitting and heater return fitting.
8. Connect the inlet heater hose onto the engine block fitting and intake manifold fitting.
9. Fill the cooling system using the specified coolant mixture.
10. Test the system for proper heater performance with the specified engine cooling system conditions.