bmwe21.net forums

The most known issue on the E21 chassis is rust! Not that strange considering yesteryears' steel quality and rust prevention, let alone the car's age!

Most common places (I hope we can get some pictures down here!)
-Top of front and rear shock towers
-Inner wheel arches & fenders front (check top and a-pillar)
-Inner wheel arches rear (check in trunk and remove rear seat to see all!)
-B-pillar around halfway
-Trunk (also remove spare wheel and check where the fuel fill pipe crosses the wheen arch)
-Around the front the windscreen, mostly bottom half
-Around the sunroof (if applicable)
-Inside the hood
-Front beams in the engine bay
-Bottom/floor (general)

Another common issue is the glovebox filling up with water after heavy rain. Either a worn windscreen seal or rust underneath it will be the cause. Be careful what you store in your glovebox!

Nice topic on removing the windows from your E21: http://www.bmwe21.net/forum/viewtopic.php?f=3&t=18614

A few pictures thanks to Peter V

Rear wheel arches







Seen from the trunk



And seen from behind the rear seat



Engine bay



B-pillar



Front footwell



Front the inside of the car, under the mat

Interior leaks at the front, footwell and glovebox area

Leaks at the front, usually resulting in wet front footwells or a glovebox pool, are usually caused by the front windscreen, well, its metal surrounding or the seal. Before we elaborate further on that, a few alternate causes:
- open hole where door wiring goes into the chassis (should have a rubber ring)
- windscreen wiper mechanism area clogged and overflowing
- bad or no plastic covers behind the door cards

In most cases however, either the metal chassis surrounding of the windscreen is rusted deep under the seal, or the seal is worn. Both are hard to see without removing. On a solid car sealant should not be necessary and usually only is a partial solution. Best is to pry out the chrome trim (it may need replacing anyway for a fresh chrome shine) and very carefully remove the windscreen with seal towards the outside so you can inspect properly.

Beware! As per 1982 BMW switched to a new (thicker) seal and a new front windscreen that is smaller in both width and height. 1. in below image is new version, 2. is old style seal. To establish what size windscreen you're dealing with, measure the windscreen height in the middle. The ones that work best with the new style seal are max 629mm.

OEM part nos:
old version 51 31 1 831 958 (-1/1982)
new version 51 31 1 904 395 (1/1982-on)