Component Tests

Heater Core

Plugged Heater Core

Check to see that the engine coolant is at the proper level. Start the engine and turn on the heater. When the engine coolant reaches operating temperature, feel the heater core (18476) outlet hose to see if it is hot. If it is not hot, the heater core is likely plugged.

1. Before heater core leak test, inspect for visible evidence of coolant leakage at the heater water hose to heater core attachments. A coolant leak at the heater water hose could follow the heater core tube to the heater core and appear as a leak in the heater core .

2. Check the system for loose hose clamps (8287) . The hose clamps should be tightened to 1.7-2.4 Nm (15-21 lb-in).

3. If leakage is found and hose clamps are over-tightened, remove heater water hose (18472) and check heater core tube for damage. Service damaged or deformed heater core tube, replace hose clamp and tighten to specification. An over-tightened hose clamp may cause leakage at hose connection.

Pressure Test

NOTE: Due to space limitations in the engine compartment, a bench test is recommended for heater core pressure testing.

1. Drain the coolant from the cooling system.

2. Disconnect the heater water hoses from the heater core tubes.

3. Install a short piece of heater water hose , approximately 101mm (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 Rotunda Pressure Tester 021-00012 or equivalent 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 Rotunda Pressure Tester 021-00012 or equivalent to the adapter.

6. Close the bleed valve at the base of the gauge and pump 207 kPa (30 psi) of air pressure into the heater core .

7. Observe the pressure gauge for a minimum of three minutes. The pressure should not drop.

8. If the pressure does not drop, no leaks are indicated.

9. If the pressure drops, check the hose connections to the core tubes for leaks. If the hoses do not leak, remove the heater core from the vehicle and test the heater core as outlined.

10. For the bench test, remove heater core from A/C evaporator housing (19850) .

11. Drain all coolant from the heater core .

12. Connect the 101mm (4-inch) test hoses with plug and adapter to the core tubes. Then connect the air pump and gauge assembly to the adapter.

13. Apply 207 kPa (30 psi) of air pressure to the heater core with Rotunda Pressure Tester 021-00012 or equivalent, and submerge the heater core in water.

14. If a leak is observed, service or replace the heater core as necessary.