2001 Aurora 3.5 that is leaking water into the floorboard of the driver's side back seat?

https://www.club3g.com/threads/water-in-driver-side-floorboard.261515/

https://repairpal.com/ac-is-leaking-water-into-the-driver-side-floor-113

Is the floor also wet under the dash? This could be a lot of things why your car is running hot. Could be a head gasket, cracked cylinder head or block, stopped or restricted radiator, water pump impeller faulty with broken vanes, stopped up heater core, cracked water jacket and or a leaking intake manifold gasket. So as I stated could be a slew of causes. You'll have to actually diagnose the cause by checking from the easiest cause to the hardest.

Is underneath your car rusted

heater core/hoses ? does coolant system level drop after you turn heater on high ?

One set is under the hood, passenger side, next to coolant reservoir. The other set is under the back seat on the drivers side.

air condition drain valve is clogged

try having an assistant 'water'' your car with a garden hose while you're in it.especially check seals at windshield & doors.it could take a few minutes of ''watering'' before a leak shows up.

if it has a back heater either a water line to the heater core broke or the heater core for te back heater sprung a leak probabley the heater core on the back heater replace either the hose or the back heater core whatever is leaking.

I recently had this repaired. As it turns out, the evaporation reservoir separated from the firewall. I was fortunate enough to have a good mechanic that completely diassembled my dash to locate the leak. He did not make up some lame diagnosis. I was unfortunate enough to have to pay for the extensive work, but it is worth it. He resealed the heater core compartment to allow the water to drain out properly. I spent many hours searching for an answer in the internet. this is the only solution that I know of.

Here is what all dealers do to find water leaks, we spray a fine mist of water on the car near where the water might be comming in with a spray nozzle, someone gets inside the car and look for the leak, there is no other way, and I have been doing this 30 years.