Heater Core

Component Test 

1. 1.
   
   
   NOTE: If a heater core leak is suspected, test the heater core by following the plugged heater core flow 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 hose to heater core attachments. A coolant leak in the heater hose could follow the heater core tube to the heater core and appear as a leak in the heater core.

1. 2.
   
   
   NOTE: Spring-type clamps are installed as original equipment. Installation and overtightening of non-specified clamps can cause leakage at the heater hose connection and damage the heater core.

   Check the integrity of the heater hose clamps.

Heater Core - Plugged 

1. 1.
   
   Check to see that the engine coolant is at the correct level.

1. 2.
   
   Start the engine and turn on the heater.

1. 3.
   
   When the engine coolant reaches operating temperature, check the heater core inlet and outlet hoses to see if they are hot.

1. 4.
   
   If the outlet only is not hot:
   • the heater core may have an air pocket.
   • the heater core may be plugged.

1. 5.
   
   If the inlet only is not hot, the thermostat may not be working correctly.

Heater Core - Pressure Test 

1. 1.
   
   
   NOTE: Due to space limitations, a bench test may be necessary for pressure testing.

   Drain the coolant from the cooling system.

1. 2.
   
   Disconnect the heater hoses from the heater core.

1. 3.
   
   Install a short piece of heater hose, approximately 101 mm (4 in) long on each heater core tube.

1. 4.
   
   Fill the heater core and heater hoses with water and install the plug BT-7422-B and the adapter BT-7422-A from the Pressure Test Kit. Secure the heater hoses, plug and adapter with hose clamps.

1. 5.
   
   Attach the pump and gauge assembly from the Pressure Test Kit to the adapter.

1. 6.
   
   Close the bleed valve at the base of the gauge. Pump 138 kPa (20 psi) of air pressure into the heater core.

1. 7.
   
   Observe the pressure gauge for a minimum of 3 minutes.

1. 8.
   
   If the pressure drops, check the heater hose connections to the core tubes for leaks. If the heater hoses do not leak, remove the heater core from the vehicle and carry out the bench test below.

Heater Core - Bench Test 

1. 1.
   
   Remove the heater core from the vehicle.

1. 2.
   
   Drain all of the coolant from the heater core.

1. 3.
   
   Connect the 101 mm (4 in) test heater hoses with plug and adapter to the core tubes. Then connect the Pressure Test Kit to the adapter.

1. 4.
   
   Apply 138 kPa (20 psi) of air pressure to the heater core. Submerge the heater core in water.

1. 5.
   
   If a leak is observed, install a new heater core.