Replacing the Seat-Tilt Mechanism

Hello!

If you're reading this, your seat-tilt mechanism has broken, and your passengers are complaining about having to get in on the same side. Worry not, for this guide will explain how to replace that rusted-out cable with little egress. First, however, it is best to list all of the parts needed for your disassembly, repair process, and reassembly. The following guide will focus on the Long Inner Cable Rope, but the steps can be replicated for the shorter side. The process is quite simple, and for a well-kept interior, it should prove a nice afternoon replacement for the average home mechanic like us.

Parts & Tools Needed

1. Vacuum Cleaner

2. Big Screwdriver

3. Small Screwdriver

4. Mini (Eyeglass) Screwdriver

5. 7mm Wrench

6. "BMW Front Seatback Unlocking Inner Cable Rope" --> 52 10 1 855 303 

7. Adjustable Pliers

8. Optional: Steel Wool (Grade 3 and Grade 0000)/Scotch Brite (for headrest)

9. Optional: Autosol Metal Polish (for headrest)

For our inner cable rope, we sourced from Roger's tii. At the time of writing, the part was only $8.54, and a picture of what was found on the website can be seen below. For quick reference, although the link may expire, you can click here to be taken directly to the page with the part. It should be noted that the BMW parts diagram shows three options for the replacement: 52 10 1 805 954, 52 10 1 849 586, and 52 10 1 855 303. Roger's appeared only to carry the latter part number.

This will be mentioned later on, but for our installation (1976 California) purposes, the wire appeared to be just a tiny bit too short. There is no doubt it will stretch over time, especially given how pressed into the fabric the original (broken) wire was, but it is something that should be noted regardless.

Repair Process

We found the best way to repair the seat was to sit in the back of the car facing forward. So, take on the role of your passengers and test out the quality of life back there! If your car is anything like ours, you will be reminded how much you need to re-stuff the rear seat as you feel those wonderful springs (ha!). With the broken cable, your best bet is to unhook the broken latch by hand (it does not take much force, even with the spring) and move the seat forward. If you do not want to do this, move to step 4, where you can remove the spring and undo the latch with no resistance. 

1. The first step in the process is removing the back of the seat. With the seat flipped up, take the screws out indicated with the three red circles. It helps immensely if you have a metal parts tray. Additionally, one of the hooks is highlighted in green to give you an example of what you would be manually lre

2. Two "hooks" beneath the headrest help hold the back of the seat in place. With the screws taken down, you pull the back of the seat out and down. A visual of the hooks can be seen below (Note: this is the proper orientation, meaning they stick up towards the headrest).

3. With the back of the seat removed, now would be a good time to grab that vacuum cleaner and clean up any horse hair that has fallen out on the floor. Often, this original stuffing disintegrates over time, creating a large mess and an uncomfortable ride. You should be greeted by an image similar to the one below. The red circles encompass the cable's path (in fact, you can see our broken and rusted one still there), while the green circle shows the pulley that redirects the cable to the far-side latch. Take this time to remove the top section (if broken) and pull the wire out from the pulley. If you are replacing the wire, it would be my recommendation to cut it if you do not care about the wire anymore. So that you know, we will take care of the rusty headrest posts later. With the back of the seat off and the area clean, we can move to step 4:

4. Remove the two trim pieces associated with the affected side. There are two screws, one for each trim piece. It is best to remove the lower trim piece first, followed by the upper piece. For the lower piece, a small right-angle bit adapter works wonders for the low-torque screw, but a small screwdriver would work as well (the driveshaft tunnel and e-brake can sometimes be a pain). The upper trim piece is delicate and breaks easily. Ideally, the upper piece should already have some side-to-side motion as you loosen the screw, but ours happened to be stuck at the bottom in a combination of dirt and rust (and lubricant?) and snapped when trying to free it.

5. Once the trim pieces are removed, you will want to remove the two big screws highlighted. They usually are Phillips, but we got away with using an adequately sized flathead and apt pressure. They stuck a bit initially, but did not show signs of being seriously stuck, and the flathead we used did not slip once. The green circle highlights where the spring normally is. It is good practice to remove this spring for easier installation; just mark which side is the top with a piece of painter's tape and set it aside.

The point of removing these two screws is the allow the spring mechanism to separate from the seat enough so that you can easily remove the old hook and install the new one. The mechanism should pull away from the seat with little force, and provide a notable gap in which the old hook and wire can be removed.

6. The old hook can be removed, and the new one can be installed. I would like to inform you that installing the new hook should take no effort or modification. With the clearance that taking out those two screws gave, the installation is extremely easy. The photo below may seem like there was no clearance with the hook end, but that is simply because of the photograph's angle.

7. The cable can now be routed vertically up the underside of the seat to the pulley. Now that the hook is in and the cable is roughly routed (not installed in the pulley yet, it is best to put two big screws back in to hold the assembly against the seat.

8. It turns out there is no room for either end of the wire rope to be fed through the pulley and shroud  because of the hook on one end and the threaded sleeve on the other. Inserting the cable into the pulley proved to be one of the most challenging aspects of this installation due to the aged, seemingly brittle-like nature of the plastic piece. We likely spent an hour carefully messing around with the wire and pulley to see what solution would work. In our experience, it turned out that using a mini- (or eyeglass) screwdriver provided enough force to push the edge of the cable over and into the pulley. From there, we were able to rotate the pulley to get the rest of the cable aligned. One of the best pieces of advice that I can give before attempting to insert the cable is to give the edges of the pulley a squeeze with your fingers. The plastic is more malleable than you might initially think and gives you more confidence moving forward with the installation. There was absolutely zero clearance between the top of our plastic pulley and the metal shroud, so we thought we were goners.

9. With the cable routed around the pulley, you can install the other end. Remember, the hook needs to be in the down or locked position when the length is set. There was one conundrum for us: the cable was just a bit too short! In other words, the perfect installed length would not include enough threads on the latch end to keep the cable fastened securely. Thus, it may be wise to wait to install after you have the length set and can check the tension by hand. Once you are happy with the adjustment, go ahead and re-install the spring and make sure the two screws are nice and tight.

The latch end nut is 7mm, and an adjustable wrench (and maybe a thin cloth, although we did not use one) can hold the cylindrical end in place.

10. Now, while everything is still off, go ahead and test the latch a couple of times to make sure it works as intended, nothing is rubbing or stuck (check inside the vertical run with your hands), and the latches close properly. If all goes well (and you don't need to get the rust off your headrest posts), close everything up in reverse order. Pat yourself on the back for a job well done!

Now, while you are replacing the cable, you may notice that your headrest posts more closely resemble cylinders of rust than metal cylinders. We used Grade 3 and Grade 0000 steel wool to clean our posts and finished with Autosol. Grade 3 may appear very coarse when shopping in the store, but Grade 0000 has almost no effective penetration and is best used as a finisher. Short of replacing the posts, it is also important to note that the posts will unlikely return to a "new" condition (unless you have professional tools). However, we obtained quite a satisfactory result with the steel wool and polishing. 

Please Enjoy Some Pictures of the Finished Results