Water in rear tail light housing.

[Big McLargeHuge]

In my opinion, I don't think drilling holes will help with the issue you're having. Your problem is water condensing from high humidity and temperature below the dew point inside of the lens, not that water is pooling on the bottom without a way to escape. If you're getting condensation inside the lens, there's already air gaps on the tops of the lenses that you've shown in the pictures above, drilling holes in the bottom will not stop that from happening and if anything just creates more area for water to enter especially from direct water sprays. No car lens is meant to have "air circulation", they're supposed to be completely sealed.

To fix that, you need to re-seal the warped taillight lenses with silicone, etc. and also install a new taillight gasket set to prevent water entering the hot trunk area and evaporating from the trunk into the lenses and condensing again. The lenses are supposed to be sealed by the taillight gaskets and lightbulb sockets, but if those are damaged or you have broken taillight studs it can allow water vapor to enter, in addition to water entering from the externally warped lenses.

If you decide to do that, I would recommend some black silicone RTV to seal the lenses which is not that noticeable if done cleanly, which you can achieve with careful masking off (better with the taillights off the car) and also wiping the silicone with your finger dampened with alcohol (isopropyl/etc.) to smooth the surface out without having it stick to your finger.

It looks like your 3rd brake light also has bad condensation issues so you might consider doing the same re-sealing at the same time. It can be removed from the spoiler by removing the caps and fasteners underneath it.

edit: was typing this up at the same time as Honcho, in agreement with that post.

 

[tomatoto]

thanks for the goods infos !
It's not totally clear to me now, as there are some technical terms (and I'm definitely not a native english speaker) and I don't really know what parts those lenses are made of, but I'm sure I will figure this out when I'll unmount them.

about the 3rd brake light, it's actually not a light... it's just painted in red. I don't know why, maybe it has been removed from the previous owner or maybe those didn't exist for the European market.


PS:Big McLargeHuge, I really don't know if I can trust someone who's using a RENAULT as an avatar ahahahah
sorry, Just kidding I really appreciate your answer !

 

[Honcho]

Thanks Joe- these are the vents to which I was referring. In truth, I don't know if it was the silicone that fixed my issue because I changed the gaskets at the same time. Could have been that. But, they've been dry ever since for the last 12 years. My bezel seams were pretty badly warped- the lens was pulled away from the black base more than 5 mm in some spots, IIRC.

 

[furinax]

Hmmm this is a good discussion. I have a gap too where it seems like that's the case. My best guess is that maybe the studs were pulled out like in Joe's #3 item. They were only taken out to install/reinstall the arc-leds which were great but had to be repaired due to water damage. It's something you really never pay attention to until you are hunting down water issues. I've never seen water buildup in my lights or trunk though.