After a year of searching and cursing, I think I've finally found the source of the leak into the drivers footwell at the bulkhead end.
I've been through all of the "usual" suspects and eliminated them:
Sunroof drains, roof join above screen, windscreen seal, plenum filter seal, screws/ bolts in plenum cover, drains from plenum area, plenum foam- then the more obscure...
door seal, side trim seal, window seal, throat seal between plenum housing and fan intake, bulkhead penetrations where cables etc go through
Still leaked- not a lot, and only when parked and the wind/ rain was in certain directions.
Got stuck in again yesterday and noticed that plenum filter was wet, but at the bottom, not the cover end. Took this pic to save me tying my neck in knots
The dirty brown area (top left) on the filter was wettest and there was standing water all around the throat area (no drains once it gets in there).
The conclusion...
The water is either coming through the wiper boss, despite all of it's seals being in place, or, more likely, wicking down the shiny new wiper link arm/ ball joint assembly that I fitted when I first got the car.
The solution...
Fit o ring to wiper shaft where it goes through its housing and put in new rubber washers slathered with silicone and
Fit a foam "drip ring" to my shiny new shaft, outside of the plenum throat area, so that water running down will just drip off into the general plenum area.
Let's see what happens :)
