The front ones drain near the back of the front wheels.
The rears drain near the front of the back wheels.

Usually what happens is that the drains in each corner
will rust where they connect to the hose that runs in the
window pillars.
If memory serves they are pretty hard to get to due to
where they are located.
You might be able to get to them once you undo the headliner
in the corners.
Mine were fine so I didn't mess with it to much so I can't remember
exactly how you get to the connections.

Louis

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Not always the smartest but certainly not dumb?