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E34 Seat "clunk"

Didn't get any suggestions on this problem but (after lots of hours) found
it, fixed it. For any of you that have the E34 with electric seats (I
believe 88 & later 7's as well) and are experiencing a slight shifting of
the driver's seat sometimes accompanied by a "clunk" sound, here's what I
found:

1-Remove seat: Tilt seat back, move head rest all the way up, remove head
rest, return seat back to a more upright position. Move seat bottom forward
 just enough to expose the two rear seat rail bolts. You'll need a "Torx"
socket to remove these and the seat belt bolt. Remove the small clip for
the seat belt tensioner cable  (under the left rear seat rail). Tilt the
rear of the seat up, disconnect the main wiring harness (large white plug,
squeeze sides to release), clip off the wire tie to release harness (be
sure to re-tie harness at installation time to prevent future entanglement
when adjusting seat). Tilt entire seat up from the rear and then forward to
unhook from the front mounting cams. Remove seat from car. 

Note: I think the rest of this is a little more comfortable if you remove
the seat back from the seat bottom. To do so is about 5 minutes. Indeed, I
prefer to remove the seat back before removing the seat from the car, makes
it easier to handle. Remove the back trim panel by removing the two lower
side Phillip's head screws (concealed beneath small plastic caps). Once the
seat back is open you will find a small lever or tang attached to a spring
on the lower portion of each side inside the seat back, by using a -large-
screwdriver, hook it under the adjacent boss, pull up on the screwdriver
(which pushes down on the tang). By prying down on the two levers (one at a
time) while lifting up on the seat back you can release each side from the
seat bottom. 

2-With the seat bottom removed, flip it upside down and set it on an old
blanket to protect the leather. There is a lot to look at under there! Look
for a stamped sheet metal "pan" that attaches the two sides together. There
will be a total of four rivets (two per side). Grab the side rail with one
hand and the center "pan" with the other and rock it looking for play at
the rivet head. In my case two rivets were "wallowed" out (wallered, in
Arkansas (<g>)). I drilled out each rivet & replaced with an 8 mm hex head
machine bolt and Loctite. 

3- While you are there, tighten all hex heads on motors, lube gear tracks.
I would also suggest unhooking the upholstery on the rear of the seat
bottom sides
(this requires removal of the hard plastic trim along where the seat
controls are) and tightening the 2 large Phillip's heads on either side. If
you do this you'll need a Torx screwdriver to remove the side plastic.

4- As they say, reinstall in reverse order.

5- Also check that the front of the seat rails are secure. Since there are
no bolts there, it is designed for an "interference" fit which can become
loose on older cars. Rather than spend the big bucks on a new assembly,
simply wedge some steel shims under there to take out any slack.

I hope this helps any one with this "loose seat" problem. I lived with it
for 5 years with my 89 535i and am really relieved to have eliminated it
from our "new" 89 525i.

Trust me, if there is --any-- movement in these rivets, it is magnified
exponentially through the seat and backrests. Although I tightened a few
other things, ALL the movement was in the rivets.

Steven C. Morey
[email protected]
Dallas, TX

BMW CCA #134873
1995 M3 (for sale)
1989 525i
1994 318is
1989 535i (remembered)
1981 633csi (remembered)