Timm's BMW E31 Boot Actuator Replacement

Includes emergency unlock instructions

This problem started when I shut the boot (trunk) and it failed to latch, the boot could be opened even if the central-locking was activated. Although the alarm would go off, this was hardly secure. A similar actuator failure could also fail to unlock the boot which could be just as annoying, although the boot could be opened using the emergency routine.

I guessed that the actuator had a problem, so here's how to get to it. First, remove the carpet on the left-hand side and move the right-hand carpet from around the CD player - remove the lower carpet.

 

Partially remove the rubber seal starting at the centre - you may find some rust here due to water ingress, I did and used WD40 on a cloth to wipe it away and to protect the area:

The plastic trim that houses the actuator is held in place with six expanding rivets. These usually have a plastic 'stalk' that is pushed through the rivet to release them, in my case the stalks were missing, someone must have been in there already! I found the easiest way to remove them was to used a screwdriver to tilt them slightly so that I could get some purchase from underneath:

When all six rivets have been removed, tilt the trim forwards so you can get access to the loom hangers, unhook the loom and remove the trim:

The actuator and lock assembly is held on by three bolts, each with three washers. Use a sharpie to mark the bolt positions:

The actuator can now be removed by moving it to the left and downwards, press the connector tangs to disconnect:

In my case, the actuator is retracting under power (when the door handle is lifted), but did not extend as it should to allow the boot to lock again. I bought a complete assembly from Ebay (£30), but decided to take it apart anyway:

The actuator is linked to the latch by this green coupling, it can be pulled apart by sliding out sideways:

It isn't designed to come apart, but a bit of screwdriver-levering and a small wound later it ripped open:

The green gear in the centre contains a clock-spring which should extend the actuator - mine was snapped where it joined to the stator:

The actuator itself can be replaced separately, it is around £90 from BMW (67111392020). I decided to use the new actuator but keep the original latch as it looked in better condition. Replacement is pretty straight-forward, align the bolts using the sharpie marks:

Remember to hook the loom into the trim panel otherwise it will not fit correctly:

With the rivets re-fitted and the trim in place, slot the carpet into the ends of the trim:

Emergency Boot Opening Procedure

While fiddling with the actuator and latch, I had a look at the emergency opening procedure and how it worked. As the actuator and latch is in the body of the car and the handle and lock is in the boot there is a mechanical link between the two for use in emergencies such as when the battery goes flat or the actuator completely fails. Here's how it works:

Put the key in the lock and turn anti-clockwise by 45-degrees:

Let the key return and then remove the key from the lock - press the button upwards:

When the lock is pressed upwards, this shaft moves downwards from this position:

To this position:

This shaft bypasses the actuator and releases the latch via this:

You can test the emergency operation at any time - using the emergency procedure does not use the actuator so the test is valid even if everything is working correctly - it's a good idea to test the procedure while you don't need it just to make sure it works!

All done, time for a cup of tea