On 2/27/2005 9:58 AM US(ET), Mark took fingers to keys, and typed the
following:

Look for water stains around the taillights and wheel wells. My 93
Sentra used to leak from the joint between the top of the left rear
wheel well and the fender, evidenced by water and mud stains running
down the wheel well from the joint. There is thick sealant covering the
joint, but it still got through somehow.

I have a 91 sentra that DID leak in the trunk- fixed it easily.
step 1- verify the leak- i sprayed it heavily around the taillights
with the garden hose, after the water drained away, carefully opened
the trunk, and did find little rivulets of water trickling down from
under the taillights from the inside.
2. unplug the taillights
3. take out the few nuts on each side that hold the lights in
4. carefully pry/pull the taillights out from the outside
5. clean up dry black sealant that is allowing the leaks as much as
possible (doesn't have to be 100% removed)
6. apply a sealant to the back of the tailight- i used clear silicone,
from a hardware store, you could find the black sealant at a parts
store, but silicone is cheap and works.
7. let sealant get a little tacky (10-15 minutes) so that the seal
will be tight
8. reinstall tails, plug in and you're done. takes about an hour total
ps- taillights are the most common leaky spot on the 91-94 sentras
-robbie