The E36 rusts in a predictable set of places, so I always know where to look.
The one that matters most is structural: the rear subframe mounts and trailing-arm pockets in the trunk floor, where the unibody sheet metal cracks and rusts and, left alone, tears loose — I always inspect this first.
Then the usual body rot:
- Rear wheel arches (inner and outer lip, where mud packs in).
- Front wings at the lower rear corner by the door.
- Door bottoms when their drains block.
- Jacking points, sills and rockers.
The water-trap spots that catch buyers out:
- Battery tray and trunk floor around it (six-cylinder cars carry the battery back there — acid plus damp rots it).
- Spare-wheel well.
- Blocked sunroof drains that soak the footwells (wet carpet is the tell).
- Windscreen and rear-screen surrounds under the trim where a chip has let go.
- The front frame rails and subframe mounts.
Prevention is dull but works: I keep the sunroof and door drains clear, and wash the arches and underbody after wet or salty roads.