Solving the tail lights water ingress for good

TL;DR who would have thought ?

Exactly one year ago, on March 8th, I was just two weeks in when I discovered that my left tail light was filled with water. You can read about it here.

By February 22nd 2025, the unit that had been replaced under manufacturer warranty was also filled with water. So I drilled it to let it drain naturally, with the idea that it would last longer dry than sealed. A pair of 2mm holes were drilled in the transparent red part at the bottom of each tail light, taking care not to reach anything inside.

As I thought it was very likely that the water came from the back of the LED units rather than the sides or the front, I went on and ordered 32mm silicone rubber caps to plug the ginormous 32mm opening hidden behind each tail light. Sure, such large holes are required in order to get the rather large connectors go from the exterior of the wings to the inside. But leaving those openings just above the rear wheels is probably not a great piece of engineering.

With the car jacked-up and the rear wheels removed, a 5.5mm allen bit is used to remove 2 screws on each tail light. A quarter-turn will unlock the large connector under each wing. It's best to hold the socket on the car firmly, or it will turn with the connector too. A small "P-clip" has to be removed using a 8mm hex socket. It's accessible only after the tail light screw is removed.

As you would expect, the black spacers and rubber gaskets were full of dirt and sand. They were thouroughly rinsed in the sink. The tail lights gently wiped clean with a wet cloth. As they were drilled, they are not saled anymore...

A central hole was drilled in each rubber cap. A slit was cut too, in order to allow the cable to get through the center.

Loose glassfiber around the holes was trimmed with a deburring tool. A rather quick job.

While the silicone caps would keep most of the water and dirt away, the fit is not perfect with holes a bit larger than expected, and we've just cut a slit in the caps.

Similar to the holes in the LED units, I thought it would be a good idea to have holes in the black plastic holders/spacers as well. As the only option was to cut small slits on the bottom edges, this was done using a small round file. The finishing is nice, I'm sure water will drain well from those.

Everything was installed back in reverse order, with the addition of the rubber caps of course. As they were too squeaky to my taste, copper grease was added to the threads.

It should keep the tail lights happy and kind of clean. I hope that's the last time we have to talk about that. But who I am kidding?