As the W123 chassis cars age, I am seeing more and more rust problems in and around the battery box. If this rust is not attended to early on, the sheet metal will completely rust out underneath the battery tray. When this happens drain water can actually leak into the passenger front foot well and end up pooling in the right rear floorboards. (So if you are having problems with wet carpets on the right side this may be the reason!)
Problem & Solution
Common among these chassis:
In my experience, there is only one product that will give you a cost effective and lasting repair for this type of rust damage. Its name is Miracle Paint. This is not a rust conversion coating or an acid. It is a porcelain like coating that adheres vigorously to rust and prevents any moisture or air from coming in contact with it again (the only way to keep rust from "growing"). When you add fiberglass cloth into the Miracle Paint you can actually bridge over holes in the sheet metal giving you strong and permanent "rust out" repairs.
If you have not done so already, you should remove your battery and inspect carefully for rust underneath. If you see visible rust plan to fix it now! Remember rust never sleeps... it just keeps growing and growing.