Heater Core - Plugged
WARNING:
The heater core inlet hose will become too hot to handle if the system is working correctly.
- Check to see that the engine coolant is at the correct 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.
- The heater core may be plugged.
- The thermostat may not be working correctly.