Hello everyone.
I have a small problem with my car. So, whenever it rains a lot, a notice that the left side cubby on the boot has water, and in the these last days, I took out the left side lining, and I noticed that, when putting my hand in the area behind the rear SAM, on the metal, this was wet.
Has anyone gone through this, or know the solution to this problem?

 

Most likely some clogged drain hole or the trunk seal.

Best way to find it is to pour a bucket of water on the affected in the area during the summer (when everything is dry) and look for the leak.

 

I’ve seen the drain and put some RTV around the sunroof drain.
The boot gasket seemed, to me, to be in good shape, but I will take a closer look.

 

I occasionally have dampness in the driver's side cubby in the trunk/boot. After reading your thread I inspected the weather stripping around the rear window and the trunk lid.

On the driver's side, it looks like this:

Note that the window weather strip doesn't overlap the rain channel on the top of the trunk.

The passenger side looks like this:

Note that the window weather strip overlaps the molding on the top of the trunk.

I know my rear window was replaced prior to my ownership because I found chunks of glass behind the trim in the trunk and behind the rear seat. The installer may have damaged the weather strip during the process.

As a temporary repair, I covered the gap with some waterproof tape.

Not the most elegant solution.

Fortunately, it is hard to detect the temporary repair with the trunk/boot lid closed.


It is raining today, but not heavily. I'll monitor this for a few weeks. If it stops the water intrusion, I'll work on a more permanent and less obvious repair.

I also found a video on YouTube of an E Class of the same vintage as our cars. The owner of that car that the water intrusion was from the taillight seal. He removed the light, applied RTV sealant around the opening and reinstalled the taillight.

Good luck solving your problem.

 

Can you upload the two first photos with a better focus? This is because I removed both side plastic trim to clean underneath and I want to verify that I installed both pieces correctly.
The rear window was replaced under my ownership, and the window seal was changed for a new one (but I'm afraid the change was done badly, even though it seemed, to me, that it was well installed).

Finally, thanks for your solution, if I cannot find the entry point , I might test your solution.

 

Here’s a better photo of the passenger side. The driver’s side is covered.

I am not sure if my car was repaired correctly. I would like to see a photo of the window weatherstrip as installed at the factory.

I can say that the driver’s side appears to have been poorly installed.

 

The picture below is how I have my window seal, and for what I’m remembering, it’s installed like the original one (the previous glass was the original to the car).



I’ve sealed the holes where the plastic rivets mount with RTV, so the next step is the taillight seal.
I also will be giving updates from my situation.

 

Why not just buy the correct rivets and other bits from the dealership for a few bucks?

 

I’ve bought the correct rivets from the dealer (I’ve bought 10, and changed them all). However, the first thinking that I had when I saw water in the cubby, and the metal behind the panelling was it could be from the holes. The only hole that doesn’t have a rivet is the one closest to the window, for the case that I have to remove this plastic again, and when I remove the rivet, one of the parts seems to disappear.
Now the rear light seal, my dealership had to confirm the availability.

 

Update: it has rain in my area and, after I put RTV in the rear light seal, it seems that no water has came inside the car (following the video on YouTube proposed in this thread).
So, at first glance, the problem was the rear light seal, that in fact was split in 2.
I also, just a few days, put my car through a auto car wash, and noticed that no water entered the car.