Zee, et. al.:

To this excellent advice, let me also add that if you've ever had a "wet carpet incident" (from either leaks along the firewall area or a clogged A/C evaporator drain), remove your front seats and center console, pull up the carpets and floor pads, and have good close look at that asphaltic insulation material that is applied to the floors. It soaks up water like a sponge and retains it for a good long time. In my '87 245, long enough for rust to form UNDERNEATH this material in all four positions (passenger and driver's side, front and rear) that it was applied. Most of this rust is surficial and I'll treat with a wire brush, metal prep and POR-15, but there are several small places where it has rusted through and must be patched. So, be advised! This is also probably a good thing to check if you're buying a used 240. If the PO or dealer won't let you pull up the carpets to inspect the floors, you probably don't want the car!