E30 seats, for some reason, are prone to problems. They fall into three areas - breakage, mechanisms faults (although these seem to be related to breakages) and fabric damage; with the former being the most common. Fortunately breakages can be welded, mechanisms swapped and fabric replaced. Other than a circlips pliers (although they can be improvised),
no special tools are required. Stripping seats is time consuming but otherwise simple.
BMW seats are modular. The base and backrest are two seperate assemblies. Non sport
seats can be built left or right handed, as can the backrests on all seats. Sports seats
have a tilt mechanism and a knee bolster which make them one or the other only.
Breakages seem to be in three general areas:
- Seatback or backrest frames
- The seat pivot
- The arms from the base that the backrest is attached to
As with any technical article where no one knows what things are called it is imperative that key items are defined at the start. I have decided to use spacial referances in this article - upper and lower with front and rear. Seats pivot at a number of places to allow backrest movement, height adjustment and tipping (for entry to the rear seats). This is accomplished through three pivot points.
The backrest pivots about the the seat base at the centre of the mechanisms for tilt/height adjustment. I refer to this as an upper rear pivot. The seat base moves via in a vertical wishbone type arrangement pivot under the base. It is pivoted front and rear and refer to them as lower pivots.
I use the word "mechanism" to describe the assembly on each side of the seat to alter backrest angle and seat height. It also includes the seat back tilt release.
In the article I may refer to items singularly but take this to mean items common on both sides of the seat where relevant.
Removing the seats:
Time per side = 5 minutes Task = World's easiest job
- If you have a 4 door car, remove the seat belt end (17mm bolt) from the side of the seat.
- Move the seat fully back. Remove the two 17mm nuts at the front of the seat runners.
- Move the seat fully forward. Tilt the seat forward and get in the back. Prise of the two plastic covers and remove the two 17mm bolts at the rear of the runners.
- Open the relevant door as wide as possible. Holding the seat at the front and rear remove it by lifting it up and rotate it out of the car.
Seperating the backrest and seat base:
Time per side = 10 minutes Task = Easy
- Remove the plastic screws on the covers over the centre of the seat mechanisms. Unhook the rear part of the cover and carefully prise the cover outwards and very slightly upwards.
- Tilt the backrest forward. Pull off the tilt handle(s) and pull, from the bottom, the cover. Remove the two screws at the base of the seat back and remove it.
- Remove the two anodized screws which hold the backrest to the support arms coming up from the base.
- Identify the two wire cables running down to the seat mechanism from the tilt lever(s). Using a narrow screwdriver lever out and up the plastic guide at the top of the mechanism.
- Bend outward the tabs on cable ends. Pull each cable slightly downwards and remove from the mechanism.
- Lift the backrest up and off.
Time per side = 5 minutes Task =
- Pop out the lever in the centre of the mechanism.
- Remove the circlip on the pivot.
- Unbolt the 17mm bolt holding the mechanism to the lower pivot.
- Lift off the mechanism paying attention to the latch towards the rear.
Seperating the seatbase and runners:
Time = 5 minutes Task = Easy
- Remove the front pivot pins. Use a screwdriver to push in the spring retainer while twisting out with a pliers.
- From this point on, avoid operating the lever which adjusts the seat (back & forth) on the runners. If you do, the runners can move different distances causing a little difficulty when putting the seats back in the car.
- Turn each runner outwards to remove them from the rear pivot bar. You do not need to remove the drawbar which runs between the runners. Watch for the two washers on each side.
Fabric and cushions:
Time = 15 minutes Task = Easy
- The seat fabrics are kept tensioned by being stretched over various metal tabs. They are obvious during removal. Pay particular attention at corners for reassembly. Sport seats have six sections while standard seats have just two.
- The sport seat base and backrest cushions (but not the side bolsters) are held in place by various bent pieces of wire. Use a pnich nose piers to both seperate and replace them.
With the seat stripped cracks and breakages should be clearly evident. Seats can be repaired by any competent welder as they are just mild steel. MIG or TIG welding is least messy. Make sure that the heat from welding does not distort the frame as it is critical that it stays square. Don't forget to paint the exposed metal afterwards.
All mechanism faults I have seen have been related to distortion of the seat frames as a result of breakage, but that does not mean that they can have faults of their own. Frame breakage causes the sides of the seat to go out of line giving rise to partial locking of the various seat adjustments.
As everything is exposed at this stage, it is easy to inspect it. Broken tilt cables can be replaced (or even improvised). Mechanisms can be swapped from dismantled cars or repaired as necessary.
Fabric repairs can be conducted by retrimmers. It is, of course, possible to swap materials from another seat but BMW stock replacement fabrics for all E30's for the good as new job.
Guess what? Reassembly is the reverse of the above - but here's some important things to remember:
- The bar for the lower rear pivot must have the two spring washers in place on the inside (see pic below) to limit freeplay. The bar is kinked and should point backwards.
- Placing the mechanisms back on can be tricky. You need to align both the seat base pivot and the lower pivot bar simultaneously (aligning the square hole first).
- The tilt stop also needs to be placed throught the rear of the mechanism.
- Don't forget the seatbelt buckle. If the mechanism is in the tilted position, it will almost be horizontal.
- For referance, here are closeups of each side.
- When replacing the covers on the mechanisms, align the small slot in the sliding cover with the tilt wire cables. Place the cover on the rear of the mechanism first, then onto the upper copper screw and pivot into place. Good luck.
- Place the cover for the seat back on by pushing the top hooks in and down. The screws can then be inserted by keeping the base pressed in.
- When putting the seats back in you may have to line up the runner tracks (if they have moved relative to one another). Having the seat adjusted rearwards will allow you to place them on the studs first.