Plugged Heater Core Test

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, carefully feel the outlet hose of the heater core. If it is not hot, the heater core may have an air pocket or may be plugged.
1. Before heater core pressure 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. The hose clamps should be tightened to 1.7-2.4 N.m (15-21 Lb-In).
3. If leakage is found and hose clamps are over-tightened, remove heater water hose and check heater core tube for damage. Service damaged or deformed heater core tube, replace hose clamp and tighten to 1.7-2.4 N.m (15-21 Lb-In). An over-tightened hose clamp may cause leakage at hose connection.