W211 Third Brake Light

[StephenSJason]

I noticed on my Dad’s E55K Saloon that some water had gotten into the boot lid, and was sloshing around in the actual opening hatch between the inner and outer metal panels; I could hear it when flipping it up and closing it down.

I couldn’t find the cause as all seals looked fine, and I drilled a small hole and drained it. No problem since as we haven’t seen rain since May however, his 3rd brake light (LED strip) in the bootlid is now out and I wonder if the cause was water ingress through there over time.

Is this a common fault with the W211 and, is there anything to keep in mind when replacing this light?

 

[AMGeed]

The third brake light is one known point of entry for water ingress on the W211 along with poor seals on both brake/stop lamp lens and worn out boot seal rubbers.
When replacing the LED unit, I would put a thin line of clear mastic around the apeture before replacing the lamp. That should rule out that area for further rain leaking in.

 

[OneForTheRoad]

theres also quite a few plastic poppers holding the whole of that plastic number plate panel in place , they have small leather type washers on them that let water in over time also . a run of silicone along the joining gap ( metal to plastic ) will eradicate ingress.