Heater Core Matrix Leak and Coolant Odour
ModerateCooling SystemThe cabin heater core matrix installed within the interior HVAC blower unit can develop hairline cracks in its aluminium tube seams and plastic tanks. When pressurized engine coolant circulates through the heater core, antifreeze seeps into the heater housing, causing oily condensation on the inside of the windscreen, sweet-smelling cabin air, and dampness under the front footwell carpets. Replacement requires a very labour-intensive full dashboard removal.
Persistent oily film forming on the inside of the windscreen when operating the demister, Strong sweet smell of hot coolant circulating through the cabin air vents, Damp or sticky carpet and underlay in the passenger or driver footwell, Gradual loss of coolant from the expansion tank without any visible leak under the bonnet
- Feel deep beneath the passenger and driver footwell carpet underlay for damp antifreeze residues
- Turn the HVAC blower to full heat and demist, observing whether the windscreen fogs up with an oily sheen
- Pressure-test the engine cooling system while cold, inspecting the cabin condensation drain tube for coolant drips