Puddle of water under passenger side rear tire

classiic HVAC failure? LHD left hand drive car , no country told.
own for how long, 2years or 1day/ or what ( right passenger door?) for rain. ingress.
you said water, well that can be clean pure water
from RAIN or HVAC evap condensate,
using AC cool or heat + defrost mode? or just pure heat mode?
I do not know what you do there
i tray to capture water,in jar,and see if it is green or yellow or pink
that is AF antifreeze,
and put my fingers in it and rub fingers to thumb and it feels very very slippery, that is AF. not water
if i sniff it and smells sweet it is AF>
(3 ways to discover AF antifreeze)
ok it's water, so dont use AC or Defrost mode.
so that be RAIN or defrost condensart
sorry i could never even guess the water gravity effects from any car made from fire wall to rear of care, gee hills even change that.
learn to do deeper inspection of all carpets there.

bad door gasket
or last drove car with say a bandanna hanging out the door.
a 1 time event,nobody can guess ever.
and allowed rain to go inside any car.
or windows were not fully up.

It is coming from the drain for the AC system under the vehicle on the passenger side bottom of the engine bulkhead from the evaporator core.

sounds like AC to me. Could be landing on a skid plate/splash shield and trailing toward the driver side.

if you have a sun roof check drain could cause water to leak inside also. sometimes a bad heater core can cause water to drain on the passenger side

that water could be the condensation line,, if you have had your AC on, water will leak from along the firewall on the passenger side, where the tube runs out of the vehicle. Your radiator could have been low to begin with and when you saw the water leak,, you though that was it. check the puddle,, is it clear water or does it have antifreeze in it? If its clear water chances are , that its just the drip line from your AC, if it does contain antifreeze , check the 2 water hoses that run into the heater core , you can also see where they go into the cab portion of the van, from under the hood,

The AC condensation drain is clogged, when the AC is on water is condensed on the cold AC evaporator core (this part is what cools the incomming air), this water drains out the bottom of the heater/AC air duct, the drain is at the bottom of the firewall under the hood on the passenger side, run a coat hangar up into the drain to clear it.

The rear ac evaporator box is not draining very well,and it is blowing the condensation up threw the vents,most likely.The drain should be under the rear passengers side wheel well.

there is a drain from the a/c housing that runs the water condensation to the outside of the vehicle, it should be on the lower passenger side of the firewall under the hood. sometimes these will clog with dirt and debris causing the condensed water from the evaporator core to build up and drain on the passenger floorboard. if it is coolant you are seeing then u have to replace the heater core.

check behind both rear tires for the a/c drain tube and which ever side it is on, the evaporator core will be in a case behind that panel

plugged drain tube on fire wall needs unplugged