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Note: This is a cheap remedy if your evaporator core housing is leaking water (condensation). It is not a fix, but it will keep your carpets from getting wet again when you are using the AC. This post has nothing to do with an evaporator core which is actually leaking refrigerant and does not address that issue at all.

My sister's '01 Rav4 L (aka "Dixie") has been accumulating water in the driver's and passenger's foot wells for some time. The water leaks were initially attributed to times of heavy rain, however there has been a persistent water leak even when no rain has occurred.

In the process of removing the stereo, I dropped a bolt and had to remove some trim on the passenger side to find it. When I was reaching around in the area under the center part of the dash, I noticed water, including a little puddle sitting on the highest point of the frame in the area, just under the AC evaporator core (aka "AC Radiator" in Toyota-speak), by the automatic transmission cable. I removed the small sheet of vinyl-topped padding (its about the size of a piece of paper), and it was soaked -- I poked around a bit more and realized that the leak was coming from the seam of the plastic housing of the AC evaporator, just near the evaporator's drain outlet. I also noticed rust in two spots in this area. The evaporator was steady leaking, dripping, even though the AC had been shut off for several hours.

I thought this might indicate a clogged evaporator drain, so I pulled the tube off and looked inside with a flashlight. Inside, there were little bits of material slightly blocking the drain, but water was still able to flow through the drain well enough. I removed the material and placed a towel under the evaporator to see how much water was accumulating from what appeared to be a leak in the housing itself.

Within a short drive period (25 minutes) with the AC blasting on high in Southern California (about 70% humidity), the towel was drenched -- we could ring it out! Water was steady dripping from the evaporator casing while also draining normally from the evaporator drain. It was apparent how water would end up all over the driver's and passenger's foot wells when driving, braking, and turning.

I determined that the housing itself was leaking water, water caused by condensation on the core from the humid air during AC use. My sister said that she uses the AC practically all the time, year-round. We have no reason to believe the core itself is leaking refrigerant, however, because her AC works exceedingly well and the pressure is fine.

The "proper" repair for this leaky housing would be either 1.) sealing the housing seam, or 2.) replacing the evaporator core all together. In consideration of these options:

1.) I'm not sure of what type of sealant to use to properly achieve this without causing some other unintended result.

2.) Her AC works perfectly and a new evaporator will cost at least several hundred dollars ($1000 from Toyota). Additionally, I'm not a fan of opening up an otherwise functioning, 17-year old AC system. I also don't have the skills or the tools for that kind of work, so it would have to be a professional job (more $$$).​

#2 was off the table right away because of cost and risk. #1 is something I would like to try later, perhaps, when I'm back in California and have some more information on a proper sealant for that application.

For the moment, we MacGyver'ed a cheap remedy intended only to prevent the water from accumulating in the cab and soaking the carpets, causing mold and rust, etc. If anyone else is experiencing an evaporator housing leak, here is what you can do about it using stuff you probably already have in your house! (Please note again -- this is for a leaking housing only, which is causing a water leak, and will have NO effect whatsoever if your core itself is leaking refrigerant.)

Here's what we did, or just skip down to the pictures:

1.) We took a plastic tupperware lid and cut it down to about 3"x5" (yellow thing in the pictures). Anything flat and rigid would work for this purpose. This lid serves as the ramp to force drainage from the leaking spot to the drain outlet. We placed the double-sided tape on various spots of the back of the "ramp" and stuck in it place such that the dripping water would have to run down the ramp towards the passenger side. We put some wadded up foil under the ramp to add additional constraint for the angle.

2.) We cut a gallon-size Ziploc about half-way down the sides to open it more, and cut off the zipper part.

3.) We cut out one corner of the Ziploc bag and inserted a tube in it. My sister happened to have an unneeded nebulizer tube, and that worked perfectly because it had a funnel-like feature on one end. We taped it with duct tape and used a small zip-tie to hold the bag in place around the tube. Any tube -- fish tank tube, cannula tube, whatever -- will work.

4.) Next we fit the bag loosely around the evaporator core housing: it doesn't need to be sealed all around, it just needs to be in place. Leaving it open at the top in places allows the water to evaporate as well as drain. We used more double-sided tape, zip-ties, and some duct tape. Just be sure that the bag is not touching the AC tube (the aluminum tube coming into the evaportor) because that tube gets very hot during the heat exchange process and might melt the bag.

5.) We put double-sided tape on the "ramp", and stuck the bag to it, being sure to avoiding making pockets in the bag where water would accumulate.

6.) We positioned everything such that the draining corner of the bag reached near the "old" drain opening in the floor. We cut a small knick in the drain grommet to accommodate the new tube, and zip-tied the new and old drain tubes side-by-side.

7.) Under the car, we again zip-tied the new drain tube to the old one, and cut to to the same length.

8.) We ran the AC on high for 15 minutes, and we could see all the water flowing out of our new drain!

Here are the before and after shots:

Its not pretty, but no one would know because this entire area is hidden by carpet and trim. We then removed the pads under the driver's and passenger's side carpet and pulled it out of the cabin entirely to let them dry. We tied up the carpet to the steering wheel and gear shifter, and dried the frame with towels. Once totally dried, it will be sprayed with Lysol to kill any mold that might have taken up residence, and dry pads will be installed.

For a little bit of time and a price tag of $0, it will do the job for now! Please add your input if you know of a way to properly seal the plastic housing along the seam.
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