heater matrix

Leaking heater matrix

If the carpet is constantly wet in the footwell and you lose coolant slowly, no doubt, the heater matrix (the actual heating element) is leaking. There are two pipes crossing the bulkhead behind the engine, on the right side. Look up beneath the lower trim panels in the cabin: the pipes go through a black box, the valve you open and close by turning the red-blue control knob on the center console. If the valve is opened, the hot coolant flows through the heating element, transferring its heat to the air blown through it.