The bulb hit water. BTDT

First thing is to drill the hole a little bigger, if you find that it isn't clogged up.

Water gets into the bulb chamber, then sloshes into the trunk. Replacing the gasket therefore has no effect. Was it the lower outer bulb? That's the one that leaks on mine.

Ultimately the whole unit must be replaced, I have never seen a way to find and fix such a leak. Only the backup lens is designed to be removed and replaced.

Remember that a tail light unit for 1986+ is not the same as older ones. The left side can be easily made to work. Right side is quite tricky. In either case you must use the newer circuit board. New part number begins with a "6".

Has to do with the conversion of the upper inner from a brake light to a fog light, and the change of the lower outer from a tail light to a tail/brake light.

Start surfing eBay, and caveat emptor.

Good Luck,

Bob

:>)