I have a '98 Land Cruiser. The back right seat belt is soaked when I try to use it. Where could this water be coming from? FYI we live in Portland OR.
Anywhere.
Water leaks are hard to back track since water tends to travel until gravity gets the better of it.
Start with the obviuous to see if you can see a way in from ; sun roof, side rain gutter welds, window weather strips.
Next, take out the headliner and see if there’s water residue tracks to follow to the inlet. ( in my house the source was 27 feet away from the drip on the ceiling )
A bright light inside would expose a hole thruugh a weld but not a weatherstrip problem.
With the headliner out, someone inside could watch while water is poured outside.
The interior in general is probably not sealed tight enough for a smoke test, but then again just disregard the smoke coming from all places below the suspect area.