Heater Core
Heater Core
Section titled “Heater Core”The heater core is a small radiator inside the HVAC box that uses engine coolant to heat the cabin air.
Symptoms of Failure
Section titled “Symptoms of Failure”- Sweet coolant smell in cabin
- Foggy windshield (coolant vapor)
- Wet passenger footwell
- Coolant level dropping without visible external leak
- Poor heater performance
Replacement
Section titled “Replacement”This is one of the most labor-intensive repairs on the E46:
- Drain coolant
- Remove entire dashboard assembly
- Remove HVAC box
- Split HVAC box to access heater core
- Replace heater core and reassemble
Considerations
Section titled “Considerations”- Budget a full day or more for this job
- Consider professional repair ($800-$1,200 at independent shop)
- Replace blend door actuators while HVAC is apart
- Flush heater core hoses during coolant system overhaul