First, watch this guy’s videos. I’m standing on the shoulders of giants, he gives a great tutorial on how to disassemble and reskin a set of manual sport seats -- heck, if you want to make entirely new skins using your old set as a template he’s got videos showing how to do that too if you’re so motivated. I wasn’t, I wrote checks.
https://youtu.be/VrdwCoTy1i0
https://youtu.be/bUuhdw4ZEcY
As good as those videos are, there’s a fair amount of differences between E30 manual seats and E28 motorized seats, so here’s what I found in doing my project:
Remove front under-seat trim by pulling the two screws. Move the seat back far enough to clear the front two bolts, remove with 17mm socket. A short extension may make things easier to reach. Using the reclining buttons move the seatback to the upright position, and the knee bolster to the closed position. Move the seat all the way forward, and then raise the rear up a few inches. Remove the rear two bolts with the 17mm socket. Pop off the small black plastic trim piece and unbolt the seatbelt harness from the frame - on the driver’s side, you may need to also unplug the wires to the seatbelt alarm if they’re not already detached.
Unplug umbilical harness at the wide flat plug in the lower left, it’s the bottom plug in this shot, you don’t need to unplug the upper one. Also unplug the smaller cable that connects to the knee bolster motor.
Tilt the entire seat either forwards, backwards, or sideways and snake the umbilical harness out from under the seat
Grasp and lift the seat out, with a straight back. Now’s your opportunity to grab all the loose change from under the seat. Go live large, who says working on old cars isn’t rewarding?
With the seat now out of the car and on the workbench, it’s time to start disassembling. Remove the seatbelt receptacle. Using a wide flat screwdriver or coin, unscrew the hinge trim retaining screw and carefully pry the hinge covers off.
Remove the two small trim screws that hold the seat back covers in place, and don’t forget/lose the trim washers. Lift out the bottom of the seat back cover, then slide it upwards to release it from its retaining hooks.
Remove the headrests by prying upwards on each headrest; a quick tug should pop them free from their sockets.
If they’re still there, remove the two black plastic push pins that hold the little flappy leather loincloth thingy that hides the motors under the seat.
Trace the wires from the headrest down through the center of the hinge and under the seat to where they connect. On my car, a PO had clipped and spliced the wires under the seat, so I just clipped the splice.
YMMV, but you’ll need to get the wires out in order to separate the seat halves. Remove the two Phillips screws that hold the back to the hinge verticals, pull the seat back up and separate the two halves.
With the seat on its side and using a Phillips driver, remove the small screw and retaining bracket that holds the drive cables in the hinge casting, then pull the drive cables straight out from the hinge.
Using snap-ring pliers or a small screwdriver, remove the circlip from the seat hinge pivot.
Using a flat screwdriver or small prybar, push back the retaining lock until it clears and rotate the seat hinge until it clears, then lift it straight off the pivot. Repeat on the other side.
The front hinge is a little more entertaining, it’s a stamped steel pin, spring and latch combination. Notice that there’s one end that’s got sort of a rectangular handle, the other open end has two small tabs. Also notice that there’s a small spring retaining tab that pokes out and keeps the pin from backing out.
You’ll need to insert a small screwdriver or pick into the pin from the open end to retract the retaining tab, then carefully tap the pin out. Your seat bottom should now be separated from the drive base. Here’s what my drive base looked like after ~30 years of collecting crap...
Flip the seat bottom upside down, unplug the knee bolster motor and snip the wire ties that hold the motor harness in place. Remove the retaining clip and pin, then pull the two Phillips screws and remove the motor assembly.
You’ll then need to remove the side trim piece that holds the knee bolster buttons. There’s a black plastic push pin that you’ll need to pry up first, then there’s two pressure fit pins that go in the side of the seat, and a large pin in a keyhole slot. Carefully pry the top of the trim away from the seat and slide it towards the back of the seat until the large pin clears the keyhole shaped hole.
Follow the steps in the video to remove all the metal hog rings that hold the foam to the seat springs. Pry up the retaining spikes and carefully pull the leather off the spikes, then slide the knee bolster outwards and remove the seat bottom cushion. Do the same for the side bolsters, then repeat all steps in the same manner for the upper seat portions.
Pull all the staples from the seat cushions, then carefully peel back and remove the old skns. Save the metal insert rods that are sleeved into the old skins, remembering which ones came from where. Mark them now with tape or other flags, so you can get things back where they belong later.
Once everything’s stripped and disassembled, you can make any needed repairs and clean up and regrease fittings. I got lucky, but I hear the welds on the seat bottom bolsters can break, so check those carefully. Replace or repair any foam cushions that are too worn to use again.
Installing new covers
When I started pulling the new skins over the foam bolsters, I really struggled at first. Then I noticed that the old seats had small pieces of thin slippery plastic over the outermost portions, they were almost the size of wide packing tape, but with no sticky and even thinner. I did a little google drilling, and found this incredible stuff http://a.co/bUIFkVB -- basically it’s ultra thin, ultra slippery plastic used to help upholster foam cushions. The really wild part is you can use a shop vac to pull the air out of a cushion and shrink it to a fraction of the original size, pop it into the cover and it will slowly expand back to fit.
I could only use that feature on the head rests and knee bolsters, but even using a layer of this stuff made it massively easier to pull the skins over the side bolsters.
Insert the metal rods into their appropriate places in the new skins, pull the skins over the bolsters and hog ring them into place on one edge, then pulling the skin tight cut a small hole aligned with the spikes and pull the skin over the spike. The video shows this far better than I can describe it, so I’m not going to repeat a lot here.
While I had the seats open, I decided to add heating pads so I could eventually have heated seats. I haven’t fully worked out the wiring yet, I don’t really like what came with the kit I got and I want to make everything look stock so I picked up a set of BMW heated seat switches from fleabay, when I get a round tuit I’ll do a writeup on that separately. But here’s what the heating pads look like, with holes cut for the seat tucks
Speaking of tucks, the original skins had a set of plastic ties that were hog ringed down to a metal rod in the foam to create the seat tuck. The new skins didn’t have the same ties, although they had a reinforced area running along the same place. I wound up using heavy duty mason line, with an upholstery needle, to create a replacement tie. I wanted to make sure things didn’t fall apart, so I used two lines in an X pattern, and used two different colors of line so I could keep track of which one I was supposed to pull on at any one time.
Using a needle nose pliers, I poked through the foam on either side of the metal rod, then grabbed the lines and pulled them through. I then smoothed and aligned the covers until everything was where it was supposed to be, then pulled the lines taut and tied them off. The original hog ring and ties had a little slack, so I used a 1/4” spacer in an attempt to give a similar amount of slack. Looking back, I think the nylon had enough give that I wouldn’t bother with the spacer again.
I always hate it when the instruction manual says simply reverse all steps to replace something, but really with the video’s help that’s kind of almost true. Final product:
