Mountaineer AWD V6-4.0L VIN K Flex Fuel (2003)
Heater Core: Testing and Inspection
Heater Core
WARNING: Carbon monoxide is colorless, odorless and dangerous. If it is necessary to operate the engine with the vehicle in a closed area
such as a garage, always use an exhaust collector to vent the exhaust gases outside the closed area.
1. NOTE: Testing of returned heater cores reveals that a large percentage of heater cores were good and did not require replacement. If a heater
core leak is suspected, the heater core must be tested by carrying out the plugged heater core component test before the heater core pressure test.
Carry out a system inspection by checking the heater system thoroughly as follows:
Inspect for evidence of coolant leakage at the heater water hose to heater core attachments. A coolant leak in the heater water hose could follow
the heater core tube to the heater core and appear as a leak in the heater core.
2. NOTE: Spring-type clamps are installed as original equipment. Installation and overtightening of non-specification clamps can cause leakage at
the heater water hose connection and damage the heater core.
Check the integrity of the heater water hose clamps.
Heater Core-Plugged
WARNING: The heater core inlet hose will become too hot to handle if the system is working correctly.
1. Check to see that the engine coolant is at the correct level.
2. Start the engine and turn on the heater.
3. When the engine coolant reaches operating temperature, feel the heater core inlet and outlet hose to see if they are hot.
If the inlet hose is not hot:
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the heater control valve may be stuck closed.
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the thermostat is not working correctly.
If the outlet hose is not hot:
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the heater core may have an air pocket.
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the heater core may be restricted or plugged.
Heater Core - Pressure Test
Use the Radiator/Heater Core Pressure Tester to perform the pressure test.
1. NOTE: Due to space limitations, a bench test may be necessary for pressure testing.
Clamp off the heater hoses.
2. Disconnect the heater water hoses from the heater core.
3. Install a short piece of heater water hose, approximately 101 mm (4 inches) long on each heater core tube.
4. Fill the heater core and heater water hoses with water and install Plug ET-7422-B and adapter BT-7422-A from the Radiator/Heater Core Pressure
Tester in the heater water hose ends. Secure the heater water hoses, plug and adapter with hose clamps.
5. Attach the pump and gauge assembly from the Radiator/Heater Core Pressure Tester to the adapter.
6. Close the bleed valve at the base of the gauge. Pump 241 kPa (35 psi) of air pressure into the heater core.
7. Observe the pressure gauge for a minimum of three minutes.
8. If the pressure drops, check the heater water hose connections to the core tubes for leaks. If the heater water hoses do not leak, remove the heater
core from the vehicle and perform the bench test.
Heater Core - Bench Test
