Heater Core Plugged

HEATER CORE PLUGGED

WARNING: Carbon monoxide gas 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. Failure to follow these instructions may result in personal injury.

NOTE: Testing of returned heater cores reveals that a large percentage of heater cores are good and did not require installation of a new heater core If a heater core leak is suspected, the heater core must be tested by following the Heater Core Plugged Component Test before the Heater Core Pressure Test, see HEATER CORE PRESSURE TEST. Carry out a system inspection by checking the heater system thoroughly as follows:

1. 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.

CAUTION: 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.

2. Check the integrity of the heater water hose clamps.

WARNING: The heater core inlet hose will become too hot to handle if the system is working correctly.

3. Check to see that the engine coolant is at the correct level.
4. Start the engine and turn on the heater.
5. 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 correctly.