Water leaking into trunk (240sx fastback)
After finding puddles of water by my spare tire, I tried for months to locate where the water was coming in.When I finally asked Nissan, they told me thathe Butyl rubber gaskets under the left and right taillights break down after about 8 years, and need to be replaced. You can do it for about $10 in parts, and about 2 hours of work.
These notes worked for my 1990 fastback but should apply to most models. Open the hatch, remove the plastic trim near the top of the trunk (four screws, two plastic inserts), then the interior piece of insulation underneath it (the grey cardboard/fabric, held in by three plastic inserts).
Remove the center plastic lens which covers the backup lights by removing the six gold nuts (8mm) holding it in place. You’llhave to tap the screws from the inside with a mallet to loosen then, then the whole lens should easily remove from the back. Next, remove the left and right side lenses, each of which is held in place by three gold bolts (8mm). On the left, you’ll have to remove a wire guide, and on the right two wire guides, to access the bolts underneath. You’ll also see four (two left, two right) bolts colored the same as your cars paint — don’t remove those, they hold on the piece of body metal below the lens assembly!
On both the left and the right side, you’ll need to remove a metal bracket which acts as a support for the interior fabric, held on by one8mm bolt; it’s next to and supported by one of the light assembly depressions. Use the mallet to loosen the screws from the back, and you’ll probably need to pry off the lens carefully with a long handle screwdriver from the back.
Once you’ve got them off, you’ll see a bunch of black goo surrounding the two lens elements on each assembly. Peel it off both the lens and the car itself, then use lighter fluid to remove any remaining residue (it’s messy, go slow when peeling it off, to try to keep it in big pieces). Go to NAPA auto parts and buy a replacement box ofButyl Rubber for windshield and lens repair. It’s made by 3M (Nissan uses the same stuff that you can buy at NAPA) and costs about $6. Unspool it and press it into the two tracks around each lens assembly on both left and rightlights. Reassemble the left and right lights onto the car, and bolt them back in place, then reinsert the wire guides (one on the left, two on the right).
Now reattach the center lens (the one that says “240sx” on it, which has the backup lights). Test all the lights to make sure everything works, then reattach the two brackets, interior trim and finally the plastic top piece.