Time to fix a fairly common issue with BMW door lock cylinders. The issue: the cylinder is kept from free spinning by a spring and plunger integrated into the door lock assembly. This spring is held under compression by a thin metal backing plate that is simply staked into place to the larger assembly. These weak stakes work themselves loose over time, eventually allowing the backing plate to fall away and the spring with it. The result is the lock will just spin freely when you turn the key. Fortunately I had already installed remote door locks before this issue occurred, so I was still able to get in and out.
I already had the doors torn apart to fix the broken glass and refresh the sliders, so this presented an opportunity to fix the door locks as well. Only the driver’s door lock had failed, but I preventively repaired the passenger door as well. The driver’s side plate was found at the bottom of the door panel, but the spring was nowhere to be found. Luckily I found a suitable spring at a local hardware store (#1 spring) which I just had to cut to length. Some claim you can weld the backing plate permanently to the lock assembly, perhaps with a more delicate TIG, but I found the metal was far to thin and my MIG, even on the lowest voltage, was just cutting right through. So my solution was to use JB Weld putty epoxy. While not as elegant, it’s sure to hold.
 First disconnect the central locking plug from the door lock. |
 There is a white plastic retaining clip that you pop out of place to unhook this metal lever. |
 The outer cover is removed by sliding a metal bar inside the door panel, a flat tip screwdriver does the job. |
 BMW has a special tool to remove this nut, but a plain pair of needle nose pliers works. |
 There is a pin and clip holding on the other side of the handle. Use a flat tip to undue this clip. |
 With the lock fished out you can see the T shaped plate as it should look. |
 This is the driver’s side plate, which had fallen into the bottom of the door. |
 The spring was no where to be found, so I picked up a #1 from the hardware store. This is it before I cut it down to the right height. |
 With the spring compressed, the plate was secured in place with JB Weld. I inserted the key to insure I had smooth operation. |
 Before reinstalling the door, I put down a bead of fresh butyl tape to secure the vapor barrier. |
at 06:38
Had the same problem with my Z3. I was a bit more lucky and found all bits and pieces inside the door. I squeezed the little T-shape plate back in its place and now hope that it will hold. By all meabs, many thanks for this advise which is very clear.
at 09:55
Henri,
I’d be a bit concerned about just replacing the T-plate and hoping it remains in place without any other device or method of securing it. It’s bound to pop off again, at least that’s what I would worry about. Glad you found the post useful. Let us know how the locks hold up!
-Chad
at 20:33
My 01 Z3 has the same issue on both doors. I will follow your instruction to fix them.
at 12:24
This is great instructions, and much appreciated.
I have similar issue on my 01 Z3 that I just bought – driver side lock will keep spinning. I haven’t yet torn apart the door panel to check the status of the spring/plate assembly, but I found that I can insert the key into the lock, press in on the lock, and turn a few times left or right to engage door lock/unlock. Whenever the day comes when this doesn’t work, I’ll make sure to follow above steps to properly fix it.