E36 320i 4 door, 1992.

This all started with a series of electrical faults - Sunroof stopped working, then the C/L on passenger side (RH drive model) stopped and then the C/L stopped all together.  This also affected the interior lighting which ad-libbed so much it was left "off". The key still worked in thedoor  locks so driving could continue.  The events above were spanned over about 6 months.  I took advice from BMW dealers, they suggested it was the "Central locking Control module".  Two dealers gave me two separate locations for this item, both were wrong as  I (And 2 scrapyards searching wrecks) never did actually find it having dismantled the vehicle!  I decided to follow the wiring from the door to the loom, this meant front seat removal.  To my surprise, the passenger footwell had at least a gallon of water in it, and the sponge of the carpet had a gallon more.  I drained and squeezed that lot out.  After much searching, again I did not find the module!  But I did find a 7-way electrical connector, near the back of the front footwell.  Upon touching it, 3 of the wires came out - full of green corrosion.  This corrosion had gone into the wires by some 3 inches too.  I cut-back, stripped and tinned the wires, joined them all up - and yep......a fully functional Central locking system along with interior lights and sunroof!  But, the main problem was the water.  How was that getting in?  I checked the drain holes in the sunroof "Guttering" and they worked fine.  I removed the interior roof lining to inspect the connector joining the down-pipe to the sunroof, which had a crimped clip on it, which seeped a little water but not enough to generate the swimming pool in my footwell.  Replaced the crimped fitting with a proper jubilee clip.  It was at this point I noticed that I could see too much daylight from this area.  Closer inspection and water testing revealed that if water could get onto the "Track" of the sunroof, it would enter the car at the front end (Near the black plate with 2 rivets on, visible from the top).  This is a design fault.  If a car is parked on a road with a camber, or driven on a road with a camber, rainwater can collect in the gutter/channel and rise to the level of the track.  If you are moving, and slow down, this water rushes forward and that which can't fit down the drain hole runs into the car.  The water tracks down the roof lining, down the front pillar lining, to the side of the glovebox (Behind the trim) and into the footwell.  As the lining and pillar lining are plastic-backed there is no sign of a leak until the footwell is full!  If you have an E36 do a check under the front carpet. 

To repair this fault, I used a sealant.  Ensuring I didn't clog up the sunroof mechanism and chain, I buried the whole area in Bathroom silicone - yep, the stuff you put round the edge of the bath.  I then replaced the roof liner to press the silicone into shape.  It certainly stopped the leak.  I then covered the external area (Track etc.) in grease.  The grease on the sunroof mechanism may attack the silicone over time, but that will take a few years.  Two problems solved in one!