The E36 rusts in a predictable set of places, so 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 — 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: keep the sunroof and door drains clear, and wash the arches and underbody after wet or salty roads.