For some time now I have been having water collecting on the floorboards in the driver's side footwell of my 1988 740 wagon with about fifty miles to go to two hundred. After reading the acrhives I removed the upper panel behind the hood and through which the winshield wipers stick. In there I found quantites of tree droppings etc. Also I realised that the mesh that should be stuck to the underside of the panel was lying in the bottom of the plenum area. I glued this up with roofing cement, (Plentiful in Florida) and it wouldn't stay, so I threaded the smallest "ty-wraps" I could find, through the mesh and behind the bars, to hold it in place. They don't look bad, so I think I'll leave them there rather than rely on the glue. My question is, where does the water go that collects in the air intake plenum, I assume I must go down the left hand side between the fender and the under body, if so have I missed an opportunity to clean it out and stop the leakage into the footwell, when I had the panel off?

Be aware that the water travel down the drivers side inner fender. If this fails the water will go to the next available place such as the blower moter and from the vent box onto the passengers side. A leak on the drivers side often does not mean anything is clogged in the drain system.

You have a leak somewhere on the inner fender. There is a plastic plug that is for an unused airvent, there are also several rubber bushings for cables and wires. Take off the plastic trim from the outside of the drivers footwell and the knee shield. Swamp the hood drain channel, inner fender and firewall with water. The leak should reveal itself. After that it is time to grab some bathroom caulk and fix the leak.

No need to take the cowl of again.

P.S I used gorilla glue to hold my mesh on. Betcha that sucker doesn't come off again.