My previous thoughts on the origin of a lot of the muck we find in the sills, been the same with both my current 75's.
"In common with a number of people on the forum I’ve had a problem with rust around the rear jacking pad, in my case the driver side. I was a little bit surprised to find corrosion in this area, because the jacking pad was still in place and the accepted wisdom seemed to be that rust was only going to appear if this was missing. Anyway I cut out the affected area, fabricated a patch and welded it into place. When I had taken off the jacking pad I noticed that one of the securing lugs was broken, so stuck some sealer around it to secure it into place, a couple of weeks later, having got a jacking pad from a scrap car I gently removed the old one, only to release a trickle of rusty water. To my mind the water was coming into the sill from somewhere else, so last weekend when I had a bit of time I pulled back the plastic wheel arch liner and found a 3 way panel join at the base of the wheel arch. The panel join is not fully closed and there is essentially a triangular opening in the centre which would appear to drain into the sill. In the case of my car the plastic liner is not a great fit and I think water would run down the inside of the wheel arch and a percentage would then be directed into the sill. The triangular opening was partially blocked by damp silt. So maybe this is the source of a lot of the mud and water that find it’s way into the sill? I’ve included a couple of photos of that of the offending panel join".
