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 proper level.
2. Start the engine and turn on the heater.
3. When the engine coolant reaches operating temperature, feel the heater core outlet hose to see if it is hot.
If it is not hot:
the heater core may have an air pocket
the heater core may be plugged, or
the thermostat is not working properly.
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.
Drain the coolant from the cooling system.
2. Disconnect the heater water hoses from the heater core. For additional information, refer to
Section 412-02
.
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 BT-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
1. Remove the heater core from the vehicle. For additional information, refer to
Section 412-02
.
2. Drain all of the coolant from the heater core.
3. Connect the 101 mm (4 inch) test heater water hoses with plug and adapter to the core tubes. Then connect the Radiator/Heater Core Pressure Tester to the adapter.
4. Apply 241 kPa (35 psi) of air pressure to the heater core. Submerge the heater core in water.
5. If a leak is observed, replace the heater core.
A/C Evaporator/Condenser Core — On Vehicle Leak Test
Page 29 of 30
1999 F-150/250 Workshop Manual
8/16/2010
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