Happy Scion 2009 XD owner here. Over the years we've noticed what seems to be a familiar complaint and explanation, which is rain water geting into the trunk area, getting suitcases wet and pooling in in the spare tire area. I've already observed how water can pour down the inside left and right edges where the rear hatch opens. It then runs under the gap where the tail light covers connect, then gets in through the wiring holes. First thing I thought was a suggestion I'd already seen and have done. I simply added a bead of clear silicone caulking along the top edges of the tail light covers. That should help but we'll see. In the mean time another part of the problem may be the long channels on either side of the roof. When the car was new, they had some kind of rubber inserts going from front to back ( I think they are called "drip moldings"?). The relentless Florida sun eventually rotted and weathered them, and when the car was re-painted 2 years ago, they were removed. I'd consider these missing parts might be exacerbating the problem, but I realize this water leaking in has been a problem for many years before they became damaged or were removed. So my first question is whether replacing them will help? And if so are there any alternatives to the OEM parts? They would be over over $100 at Toyota!

Also, when I realized water actually was actually pooling in the spare tire well, I noticed there was a convenient rubber plug. The plug is perfectly placed at the lowest point, and popping it out quickly allowed the water to drain. So until (and unless) I can prevent water from getting in there, can anyone tell me any reason I shouldn't just leave that plug off? Seems like an obvious preventative measure, but maybe I'm missing something? What's the worst that could happen? A mouse crawling in there? I guess I could leave the plug off but cover the hole with a piece of aluminum window screen right?

 

There is a gasket behind both rear light housing that when worn will let water in. Replace those. For my xA, they were about $20 each so $40 for the set. It took me all of 10 minutes to replace those and no more water in my tire well. Hope this helps.

https://parts.lakelandtoyota.com/p/S...155252670.html
https://parts.lakelandtoyota.com/p/S...156252600.html

 

Thanks! Well at least I now know there is a correct solution! I was always glad I didn't need to take those covers off to replace bulbs because like a lot of things in my XD, there's always one bolt or screw that no tool I have can actually get to. But if my bead of silicone doesn't work 100%, I'll try again.

 

wait, you put silicone ....where?