R rear quarter panel lens 07 XK
 

The lens that was in the car when I purchased was cracked. I finally replaced it a couple weeks ago with a used unit via car-part.com. Unfortunately, though there are no visible cracks, the seal is allowing condensation. The parts store is sending me another, but I got to wondering, has anyone had or know of a problem with the RH rear lens being a problem on the XK? Just curious.

As an aside, I replaced the pigtail because one of the two metal connection prongs within the brake light socket in my original unit broke upon cleaning. 🤦🏻

Yours is the first I’ve heard of regarding moisture in taillights.

Mine was cracked at the horizontal seam where the amber and red meet. I fixed it by wrapping the entire lense area with a glossy clear vinyl wrap. Essentially sealing it. A few months later I replaced the set with LED tails because the opportunity came up. The problem with the early lenses was the adhesion of plastic where amber and red meet. They only crack due to light impact if lets say it gets bumped into with light force. The crack is nearly invisible, but if you press your finger into the plastic lense near the seam you can clearly see where its perfectly cracked. When I joined the XKR forums several guys had the same issue. Perhaps theyre no longer members.

When I got my car it had water showing in one rear lens. I took it off and dried it out indoors for a few days, but the first time it rained it showed again. There were no visible cracks or holes, so I sealed it and pressure tested it like an inner tube The entire seal down the corner between two lense colours was unsealed. I wiped a tiny amount of black bostic sealant into the seam with my thumb, and it has been perfect ever since.

Thank you! While the used parts vendor is sending me a replacement, in the interim I'll remove the lens and look with my magnifying loops to see if I can locate a crack. The Jag guy who tends to my E type suggested filling the lens with water to see if I could determine the source of the leak.

Good to know, I will check that area! Much appreciated.

I would think filling the lens with water wouldn’t be great for the electrical sockets.
Maybe use a smoke machine to see if smoke exits a crack. Or try a little air pressurization inside the lens as Jaunty did and spray the lens exterior with soapy water to see if bubbles reveal a crack.

Oh jeez, I should've been a little clearer there! I would remove the lens from the car, extract the the bulbs and disconnect the pigtail from the socket / rear panel and put aside indoors. That said, I like the air pressure idea much better, that seems perfect. I was unclear how Jaunty did that till you explained it! Thank you!