Rust
Rust is the biggest killer of any car, and E30s are no different. As perfectly constructed as they are, the ravages of time can't be held back and your car will at some point develop the dreaded tin worm.
When the brown starts poking through, consult this guide to see just what horrors could lurk underneath...
Contents
Front Arches
After years of abuse from grit, mud and road salt, the front arches will turn crusty and bubbly. Because of the inner lip of the arch, rust will develop from the back and by the time it has bubbled through to the paintwork, it will be a nasty cancerous patch all around the edge of the arch.
Repair patches are still available, and new metal can be let in fairly simply.
Front Wing
Aside from the arches, the front wings on E30s are also prone to rust at their lowest point, especially if a body kit is fitted. The smallest amount of bubbling will usually reveal that the entire mounting bolt area has rotted away, and that the wing is only being held in by two bolts on the inner arch. While a repair panel can be fabricated, it might make more sense to replace the entire wing, since they are easily detachable.
Front Inner Wing
The Inner wing, especially the flitch that supports it, can rust from behind the plastic wheel arch guard, and go un-noticed for years. The only signs will be scabbing along the top edge of the wing where it's bolted, inside the bonnet. If you see rusting along that edge, get the wing off and inspect immediately.
The repair can be made in situ, as long as it hasn't spread to the bulkhead.
Front Suspension Turret
The inner wing sits on top of a much more sturdy metal plate which forms the base of the suspension turret. Over time, water seeps in between these two skins and rots out the turret from the inside out.
It is possible to cut out and repair the thin sheet metal, since this usually doesn't affect the structure of the turret itself, but if the crack spreads too far it weakens the strength of the inner wing.
Rear Arches
Rear Inner Arch
Sills
Inner Sills
Scuttle
Roof
Sunroof
Floor
Bulkhead
Bulkhead rust is most evident as water leaking down behind the glovebox (or pedal area on LHD cars), leading to orange staining. It should also be seen as a spreading crack underneath the fuse box (seen with fuse box removed).
This can be one of the most problematic repairs, since the wiring loom travels through this area, and cannot be removed without stripping the interior entirely. However, lots of small patches will allow you to slowly rebuild the holes left behind, but will require more exploratory cutting to find the true extent of the problem.
