Wet Rear Passenger Floor Board (Not Rain!)

[total1]

1997 ES300 @ 135K

We have a VERY VERY wet passenger rear floor board!

At first we thought it was due to a water bottle that had tipped over during a trip. We didn't know then and now we're strongly leaning towards an air conditioning (AC) issue.

We recently had our Expansion Valve replaced on our ES300 when our AC when out a couple of months ago in 100+ heat. After driving the car for a couple days on a trip we noticed the rear passenger floor board was wet. Thinking a water bottle had tipped over we never gave it another thought. Then, on another trip we had a wet rear floor board and still thought of the possibility of a leaky water bottle but none of the water bottles showed any loss of water. On our way home in another 100+ trip we noticed a serious amount of water (more than previously) in the rear passenger floor board but we didn't have any water bottles nearby nor was it raining outside at anytime during our trip. [Windows up, no rain, AC set at 74-76F with level-2 to level-3 AC fan speed]. This situation happened both days on this trip. We soaked up the water wringing a hand towel 3+ times of water in this area! ;-( We did this at several stops during the day on the trip!

1) What could have caused this?

2) How do I fix it?

3) What are the implications of any consequential issues here (rust, shorting of wires, carpet etc)?

4) We've also noticed that our remote trunk opener doesn't work any longer nor does the trunk button to the left of the steering column. How can I fix these issues?

TIA

[landar]

Personally, I think it might be gremlins. They can be very devious fellows.

So, the rear passenger carpet is soaked but not the front passenger carpet? This *should* be a very easy find. I do not see how water from the A/C gets to the rear w/o also soaking the front. I rule that one out. Then, with no rain, it cannot be outside getting in. It must be something leaking from a container within. As much as you do not think a bottle or cooler or whatever is leaking...it must be.

Does the rear carpet get wet on a daily basis or only on a trip? Someone spilled something and is not fessing up.

[gbhrps]

If you are certain there has been no rain that could cause the wet rear carpet issues ........... those usually come from the plugged/disconnected/split sunroof drain tubes that allow water into the rear seat and trunk area, ....... then the only other entrance for water is from your HVAC unit.

In your case it may be that the drain is plugged, allowing water to back up and dump on the floor of the front passenger carpet. Then when accelerating, when enough water has built up, the water flows back into the rear footwell where it accumulates. I suspect that your front carpet (passenger side) is wet as well.

There is a plastic/rubber drain tube (about 1/2 inch in diameter, sometimes corrugated) that takes water from the bottom of the heater box, and exits through the firewall on the passenger side of the car.

Look under the hood on the passenger side, on the firewall, near the bottom, you will find a rubber hose nozzle. If it is plugged, clean it out. Sometimes just squeezing it several times will open it up. (Old age and heat and grime do the plugging up.)

Other times you'll find that the tube has come disconnected from the bottom of the heater box, or split. Look on the passenger side footwell inside the car for the bottom of the heater fan assembly. The tube will go from the bottom of the fan box to a hole in the firewall. Make sure its not plugged, etc., etc.

You may find that the bottom of the fan box has plugged up with dirt near the drain, and it'll need cleaning as well. Good Luck!

[lexis lexus]

I find the coincidence of this happening after the expansion valve was replaced, suggests a causal relationship. One possibility is that whoever did the job, didn't wrap up the expansion valve in it's foam encasement, leading to condensation along the valve and dripping downward and backward. Doesn't explain the dry front wheel well, but does explain why it happens on a long trip.

But coincidence doesn't necessarily lead to causality. Still the best explanation, rain or not, is that the sunroof drains are blocked and there is overflow into the back seat. This has happened to me a few times when I park the car on a slight grade with the passenger side lower than the driver's side, and then it rains. When I accelerate, there's a whoose of water which eventually ends up in the right rear wheel well.

LL

[gghee]

I own a 2023 Lexus ES350 and I am finding the floor board in the right back passenger side soak and wet after using my air-conditioning.   I tested the leaking sun-roof theory and that was not it.  I also left the car sitting in a very hard rain-storm and that was not it,  It seems to be directly related to the air-conditioning.  

The issue with this is that if it is coolant, that solution is very dangerous when inhaled.  I wonder why this seems to be an issue with these vehicles.   

Edited March 21 by gghee