Heater Core: Testing and Inspection

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.

The heater core is an all-aluminum core which has two rows of flat tubes to maximize engine coolant flow. It is located in the A/C evaporator housing in the passenger compartment under the instrument panel.

1. NOTE: Testing of returned heater cores reveals that a large percentage of heater cores are good and should not have been replaced. If a heater core leak is suspected, it should be tested as described in the Plugged Heater Core procedures before removing the heater core. Perform a system inspection by checking the heater system thoroughly as follows:
Inspect for visible 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. Check integrity of the heater water hose clamps.
3. Spring-type clamps are installed as original equipment. Installation and over-tightening of non-specified clamps can cause leakage at the heater water hose connection and damage the heater core tube.

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 outlet hose to see if it is hot. If it is not hot, the heater core may have an air pocket or may be plugged, or the thermostat is not working properly.





Pressure Test
Use Rotunda Radiator Pressure Tester 014-Ri 069 or equivalent to perform pressure test.

1. NOTE: Due to space limitations, a bench test may be necessary for pressure testing.
Drain the coolant from the cooling system. Refer to Cooling System.
2. Disconnect the heater water hoses from the heater core tubes.
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 Rotunda Radiator Pressure Tester 014-R1069 or equivalent in the heater water hose ends. Secure the heater water hoses, plug and adapter with hose clamps tightened to 1.7-2.4 N.m (16-21 lb-in).
5. Attach the pump and gauge assembly from Rotunda Radiator Pressure Tester 014-R1069 or equivalent to the adapter.
6. Close the bleed valve at the base of the gauge and pump 241 kPa (35 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 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.





Bench Test
Use Rotunda Radiator Pressure Tester 014-R1069 or equivalent to perform bench test.
1. Drain all coolant from the heater core.
2. Remove heater core from the A/C evaporator housing.
3. Connect the 101 mm (4 inch) test heater water hoses with plug and adapter to the core tubes. Then connect the Rotunda Radiator Pressure Tester 0 1 4-R 1069 or equivalent 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, service or replace the heater core (as necessary).
6. Install heater core into A/C evaporator housing.