I have been chasing this problem for months on and off. I travel for work so I can't dedicate a ton of time in a row to it. I pulled the carpet floor up and both the front passenger and driver side were wet and moldy. I left them up sprayed them with Clorox and left a fan in the car for 2 days. Then I ozoned the car. This seem to get rid of the smell. I had heard that the sunroof drains get clogged and can cause this to happen so I tested them and the driver side one was definitely restricted in flow. I used a keyboard compressed air can to clean it out and the flow was a lot nicer afterwards.

I thought I had figured it out and remedied the issue but 3 days later it rained and the smell came back some, so I pulled up the driver side carpet and it had gotten a little wet on the outboard side of it. I used a hose on different areas of the external driver side area and the roof to see if I could recreate it but I could not. The sunroof seal was definitely leaking so I have a new one coming but I don't think that's where the water came from since the drains were doing their job.

I was hoping someone would have input on where else water could be coming from to get in the car. Thank you for any help.

 

I think it is still from a partially clogged sunroof drain, or, less likely, a clogged air conditioner drain.
The compressed air was probably not strong enough to completely clean the sunroof drain. You need to get a sunroof drain cleaning tool from Amazon which costs about $7. It is a small brush on the end of a flexible semi stiff wire. Just search sunroof drain cleaning tool on Amazon. They work quite well. I have the one titled Long Wire or Long Drain etc.
You can also use Weed Wacker Line, but this tool works better because of the brush.

 

Two things here.
Prevent entry of water:
If you can see/access the drain hole, run the grass trimmer line through it.
Check for leaks around the windshield.
Make sure the cowl [the transition area light below the windshield] does not have any leaves etc which are preventing drainage.
Verify that the AC condensate is not entering the cabin.

Airing it out
Explore in the trunk and make sure it is bone dry. Standing water there will slow down the dry out time.
If you have a garage, leave the windows open to air out.
Remove add on carpets to expose attached material to air.
Drive a bit more as there is forced air flow when the vehicle is run. Run on high heat with windows open.
Take advantage of hot sun [crack the windows a bit]. Leave couple of sheets of Bounce [your favorite fragrance] etc [don't leave it on leather]/dash].
Run with A/C on even when cold to reduce moisture .... [defrost mode].


Salim

 

I have the same tool that Clutchless referred to. Using it twice a year keeps the sunroof drains clear in my wife's 2015 RX350 and my 2013 Subaru Outback 3.6R. Quick and easy to do. Just remember to use it before you actually need to and your interior carpets will stay dry.

 

Thanks! Do you use this on the rear sunroof drains as well? I'm still trying to figure out how to get to them.

 

A lot of forums and YouTube videos will tell you it’s the AC, sunroof, or some other drainage issue.

The fact is the roof rails leak. It’s happened to three Lexus or Toyota vehicles I’ve owned: RX350, 4Runner, and LX570. I just bought the LX 570 used yesterday and this morning I spotted mold and smelled mildew, which I didn’t notice yesterday because it was cold. There’s no amount of Lysol, vinegar, etc. you can use that will fix the mold until you stop the leak.

This is a serious issue toyota has ignored. I’m returning the Lexus tomorrow and never buying a Toyota or Lexus. So much for reliability :/

 

Getting at the rear sunroof drains is a time consuming adventure and involves taking apart the rear side panels in the hatch area. You may want to skip this unless you have water back there. See this link to a thread about it and at post 3 there are links to 3 more threads which tell you exactly how to do the rear drains along with photos. https://www.clublexus.com/forums/rx-...ure-issue.html

 

Much less likely... But... Is there a chance your sealing around the windshield is compromised? Any rust bubbles showing around the windshield?