Water entering via rear heat vent

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.

Hi Water leaks can be a pain to solve. There are three possibles (1) Main cause obviously water comming in from outside ie, rain or driving through mass water on the road. (2) Water coming from cooling system entering via the heater at front. (3) air conditioner unit normally the drain leaking back into car. Because the floor slopes to the rear don't rule out the fault being at the front. If your engine has coolant in the cooling system water entering from cooling system will have a sweet smell if no smell you can normaly rule out the heater leaking however check level of coolant Make sure engine is cold. If you run your hands around the heater unit front centre inside car check for any wetness around heater and carpet. If these areas are all ok its a matter of hunting down a leak from outside. You will need a second person to spray the car with a hose whilst the other sits in the car and checks all possible areas. There are no known areas for water leaks but due to the age of the vehicle check for any cracked or shrunken rubber seals. Good luck

Check for leafs that are blocking drain holes on both ends . Air inlet cowl in front of wind shield. This blockage would cause water to back up and enter the Hvac air inlet.

You have one of 4 problems, #1 the drain at the bottom of the plenum is clogged (this usually drains out under the car near the fire wall on passenger side if vehicle and is useful primarily during AC use to drain condensed water) #2 your heater core is leaking and requires replacement. #3, the outside air intake venting is not draining properly and allowing rain water and condensation to enter through the intake and into the plenum. #4 in rare cases coolant is leaking past the heater hose clamps at the heater core and allowing coolant to enter the plenum.

you maybe right. check the air vents outside of the vehicle under the windshield wipers, also check the rubber seals around the passenger door, and window.

if you have a sunroof in this you drain tubes are probably plugged. you would need to remove the headliner to check.

I have a 1993 ParK Avenue, the original owner said that when she purrchased the vehicle new in 1993, she has always had water getting into the trunk, I found water in the passenger rear floor and I assume it is through the trunk, I had water in the trunk, I drilled holes in the trunk , also in the floor of the passenger area, Yesterday I vaccuum the car and the passenger area was dry, I think a little water may enter the trunk but it will drain before it reaches the interior.

It could be a plain old fashioned leak around the windscreen - difficult to find but try sitting in the car while somebody plays a water hose over the windscreen.

It could also be a blocked drain in the ventilation system - fresh air is normally drawn in to a car via vents at the bottom of the windscreen. These vents normally lead to a "box" like structure where any water that enters the vents drops to the bottom and then drains away via a short hose that runs to somewhere underneath the car.
If the drain outlet or hose gets blocked (by leaves for example), it can cause the box to fill with water to the point where it can leak out in to the passenger area.

Hope this helps you find the problem.

Is it possible the water is actually coming from the A/C evaporator case, whose DRAIN IS CLOGGED ? The water produced by the A/C then leaks out of the case, down under the carpeting, then depending how vehicle is parked, can flow to the rear floors and carpet. Hope this helps

I have the same problem with my 91' 318. Water is coming in from the outside air intake at the base of the front windshield, under the black vent covers. If the basin fills up, water enters the vent system throught the outside air intake. Solution: there is a drain line at the fire wall, easily accessible between the firewall and engine block. It drains water from the basin. It becomes clogged with dirt, and prevents water from draining. However, after further inspection of mine I noticed that during periods of HEAVY rain, even a clean drain line is inadequate to drain that volume of water and the same happens. See attached link. Good Luck

http://e30.bmwdiy.info/passenger-water-leak/index.html