My old boss's wife had a S320. His evaporator died out of warranty, and I believe that it cost him around $4k to fix it. 23 hours of labor, $1000+ in parts.

If it's the long wheelbase version, it might (not sure) have hydraulic load-leveling shocks in the rear. These are failure items, and cost quite a bit.

I've read that the soft-close door feature can cost a bit when it breaks as well.

The 6 cylinder in that car will need a head gasket sooner or later as well.

All in all, W140s are very nice cars, but expensive to own out of warranty. I chose my W124 to try and stay away from the really big bills (but my evaporator still went to the tune of $2000).

best of Luck,
Troy
1995 E420 83k