2006 Gs450H Evaporator Drain Issue (And A Fix)

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I just thought I'd document my experiences with the evaporator drain on my 2006 GS450h. Apologies in advance for the long post...

I first noticed the issue when I found that condensation was appearing on the inside of the windows of the car. This is always a sure sign that there is water in the interior of the car.

Initial searches failed to find anything until I decided to lift the rear carpets of the car. When I did so I found the sound deadening foam and underside of the carpet completely saturated. This is a common enough phenonmen due to the waterproof nature of the carpets preventing such water reaching up. There was probably 1.5 litres of water in total in each side.

Having researched the issue through the web, I found that the air-con evaporator drain on the 2006 GS models is a known issue, with the drain becoming blocked and the condensate, which would normally puddle under the car, instead drains directly into the car interior. In hindsight, I don't recall ever seeing a pool of condensate under the car in the past.

I was lucky (I think) that only the rear carpets were wet. The carpets and underlay under the front seats was mostly dry.

There are many great posts on the various Lexus sites describing the issue and detailing how it can be addressed.

The evaporator drain is on the "roof" of the transmission tunnel and is designed to allow the water to drain onto the gearbox and run down to the ground.

There are a number of TSBs from Toyota and the latest ones describe how to remove the offending drain grommet by yanking it out with a pliers from below the car. I think the most recent TSB for this issue is the following: word)/attach/u/7cff5226.pdf

While this can be done for the IS and GS300 and GS350 models, it seems the fix for the GS450h remains to remove the evaporator unit and replace the drain grommet with a new one. This requires complete removal of the dash and console and was not an option for me.

The method recommended in the TSBs for the IS and GS models is to disconnect the exhausts, loosen the rear gearbox crossmember and lower the rear of the gearbox until the grommet can be accessed and removed with a set of long pliers.

Some people have commented that it is possible to remove the grommet without lowering the gearbox or loosening the exhaust.

Having worked on the GS450h, I believe this option of lowering the transmission will probably not work for the 450h. The "gearbox" on the 450h appears to almost completely fill the transmission tunnel. In addition, the GS450h has a cladding on the interior of the tunnel, further restricting access. This cladding is about 10mm thick and is bonded to the tunnel and does not appear to be fitted to the IS or other GS models. There is about 15mm of clearance along the sides of the gearbox.

Even if the gearbox was lowered and the heatshields removed, I don't think it would be possible to reach around the gearbox to access the grommet as the gearbox on the GS450h is very tall.

Here's what I did. I was lucky to have access to a pit to do this work, but a 4-post lift of some kind would be even better.

I removed the lower tray under the gearbox (2 nuts, 4 screws).

The first challenge is to locate the position of the grommet. It is not possible to see it directly at all from under the car.

I used the "endoscope" I bought from Lidl some time ago to locate the grommet. The position as detailed in the TSBs is confusing and I was eventually able to find two photographs on the web which helped me locate the position.

For reference, the grommet is in the roof of the tunnel, roughly in line with the support bar providing support to the exhausts. In the attached photos, you can see the flexible portion of the boroscope taped to the support bar for the exhausts.


If this sounds easy, it took me one day to locate the grommet with the endoscope! Part of this was because I did not know where to look and partly to the quality of the Lidl endoscope (I think it was €75 a couple of years ago).

The Lidl boroscope requires that the camera is about 10mm from the area you want to look at. I imagine a better quality scope would provide better lighting and have a camera that would allow a wider view.

I believe the cladding on the transmission tunnel also makes it more difficult as the grommet is further recessed in a cutout of this cladding compared to cars without the cladding.

I taped the scope in position when I had the grommet in view as even the smallest move meant the grommet disappeared from view!

Once I had the grommet in view, I then had to access it.

I first used a long gas welding rod to create a tool I could use to probe for the grommet.

To access the grommet, it was easier to come from the front of the gearbox, coming from the alloy crossmember, and feeding the wire across the top of the gearbox. I don't think it would be possible to do this from the side of the gearbox.

When I located the grommet with the wire (quick to say, but it took at least an hour to even see the end of the rod in the boroscope screen...), I touched the grommet and about 1/2 cup of water came out!

I don't think the grommet was blocked with debris, but had just sealed itself, perhaps due to little use of the car over a period of weeks. It might be the case that closing all the vents, stopping the heater channels under the front seats and turning the fan up full might have opened the drain....

Even given the access and means to reach it, it would be still impossible to remove the grommet. I just needed to rip it up as much as possible.

To do this I created another tool using copper brake pipe I have from other projects. I basically replicated the shape of the initial tool and flattened and created a barb on the end of the tool to rip the grommet.


The copper piping allowed the tool to be stiffer than the welding row, but with enough flexibility to allow it to be manvoured into place. With practice, I could locate the grommet first time, almost! Coming from the front of the gearbox allowed me to use my hand higher up to brace the piping as I moved the end of the pipe to rip the grommet.

I think I was able to rip the grommet sufficiently so that it won't be a problem again.

After I did all this, I ran the air-con at full cooling and was pleased to see a stream of water from the drain.

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thats good news mate i have never seen condensate under my car and always thought mine was blocked but ive had no misting in car and carpets are not wet but i have got that doubt in my mind i may ask garage next service and print of your solution if that is ok



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If I can provide any additional information, please let me know.

Before I started the job, I had hoped I'd be able to take lots of pictures and provide a precise location and view of the offending grommet, however with the tight access etc. I found it impossible to take any meaningful images.

A better quality boroscope, with better lighting, would probably make the biggest difference as locating the grommet was the single biggest hassle I had.

Given the size of the gearbox and the available space, I don't think loosening anything would be of any benefit. Given the state of the exhaust bolts etc. on my car I would be afraid to move anything on the exhausts for fear of breaking flanges, pipes etc.

Just a note. When checking the carpets etc. it may be necessary to actually lift the carpet to check underneath. On my car, the top of the carpet felt barely damp and it was only when I lifted the sill cover (it can be lifted without tools but is very tight) and checked below that I discovered the extent of the issue.

If you're not experiencing any misting on the inside of the window, then I think you may be OK. As the condensate itself drips onto a hot gearbox/motor/generator (I'm not sure why Lexus thought that a good idea) it may be the case that a pool of condensate on the ground would be rare when the car as irruning as it probably evaporates from there.

Best of luck.

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yes you maybe right as the system runs perfectly it was just that i have never ever seen any condensate under the car maybe others have but i do take your point about hot gearbox /exhaust etc

But ill still get them to check on next service

thanks for reply


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That was a very helpful guide, thank you very much :)

I think I may have to attempt this on my GS soon. It too has had a spell of damp carpet along with condensation on the left windows.

It does however have the approved pre-owned 3-year warranty on it, so I'm going to attempt my luck and see how much it'll cost to do it via the "official" route at Lexus 1st.

Cavanman01, what was the size of your barb and how much prodding and force did it take to rip the grommet?

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Hi Cavanman, thank God for your post! i am in the same problem, and lowered the transmission but wasn't able to find the grommet. Called Lexus melbourne and they said have to remove dashboard which is a absolute massive job.

Now i am just waiting for the borescope to arrive from ebay, then i can start rippppping the grommet!

Any tips on how to locate the grommet? i am guessing its middle of your copper wire and the endoscope?


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