Passenger Compartment Leaks
A leaking heater core or a clogged drip tube result in puddling on the passenger's compartment floorboard. The heater core is located under the dash, in the passenger's side, or the center console, inside the air distribution case. It's part of the cabin temperature system and part of the engine's cooling system. It transfers heat from the engine's coolant to the passenger's compartment. Depending on the system, this flow may be controlled with a heater control valve or flow continually whenever the engine is running.
If a leak occurs in the heater core, the coolant leaks onto the front floorboard of the vehicle. It may also drip out of the vehicle's evaporator drip tube and seen on the shop floor or the customer's driveway. Leaking coolant results in a sweet smell, especially in defrost. It can also fog the windshield. Check the vehicle's coolant reservoir; if it's low, pressure test, and inspect the heater core.
The drain tube located at the base of the air distribution case can become clogged, preventing moisture from draining from the case. Instead of draining outside of the vehicle, it collects in the case and drips onto the floorboard. This clog results in a wet carpet on the passenger's side of the vehicle. Sometimes they can be unclogged with an evaporator cleaning kit and a piece of flexible wire. Be careful not to poke a hole into or damage the fragile evaporator core.