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Sealing a tail light (yes I've searched!)

5 December 2018
I know this has been discussed before and I have searched, but can't find any photos of this as past discussions are all too old.

Real quick background:
- I get condensation in my left tail light and centre garnish piece, and water in my trunk
- I have replaced all tail light gaskets
- after experimentation I can see that water is getting into the tail light if I blast the area with a hose, the tail light fills up to about a third until it overflows into the trunk. The water in the trunk warms up from the exhaust and makes a very humid environment, the warm humid air goes through the tiny ventilation hole into the centre garnish, and then condenses later as it cools

So, the solution is to seal the tail light and let the centre garnish dry out, which takes weeks because that hole is so tiny.

I see plenty of people have talked about sealing their tail light with a clear sealant but no amount of searching I've been able to do shows where to seal.

People say that the black part and clear red part warp and separate, I can see that happening here:

However that's just a removable trim piece:

Is the bit people seal between the black and the red clear plastic on top here? Mine doesn't appear to have bowed or opened up so I can't work out where the water is actually getting in.
I did search and saw all of those threads, none of those actually answer the question as to where people run the silicon or where the tail lights actually open up. The closest in those was people talking about sealing between the black plastic and the red clear part but they did it to the very top piece that is just a removable part and from what I can tell doesn't actually seal anything... it's just a trim piece screwed on to the housing.
Opening up the tail light

and you have JDM lamps with a clear cover....not seen in USDM. So take lots of photos...


If you don't want to separate the plastic: tape up on each side of the joint between the translucent plastic and the black ABS, apply RTV/silicone on the transition valley, and pull up the tape before drying. You can use alcohol to smooth. You might try using a flowable sealant (Dowsil 734).

The foam gaskets might be your problem as the water drips behind the taillight and gets past the lamp plugs. You have to spend a lot of time progressively torquing the nuts to get a nice seal. It may be that your lamps are warped too...