BMW Repair: door latch sticks when cold, door latch, silicone oil

Question
Hi Tino,
I have a 1998 328i and am having trouble with the doors not closing when outside temperatures are near freezing. Usually I can jiggle the hook-shaped latch that engages to actually close the door and it will work. However, tonight it is very cold (30 F) and I am unable to move the latch on my driver's side door at all, even with tools. (I'm referring to the latch on the side of the door, not the door handles.) The door will not close at all.

Do you think something simple can repair this, such as grease, or do you think it's mechanical? It has happened on 3 out of 4 doors, but this is the first time a latch has truly stuck. Thanks for your help.
Brittany

Answer
Hi Brittany!
Locks do freeze up during cold weather. But old locks also
get wornout and have to be replaced.
Assuming that it is not broken or wornout and that it has just seized-up, it is best to bring the lock to a slightly higher temperature (probably with a hair dryer set to heat), then clean/spray the lock with brake cleaner, and then lube preferably with silicone oil spray or light oil (not grease since grease easily freezes. Spray the key hole also with silicone.
Then test movement by alternately---
a) using the key to test movement of the lock indicator at the top of the door (meaning both remote unlocking and manual keyhole unlocking)
b) moving the inside door lock lever
c) moving the outside door handle lock lever
d) moving the lock's hook on the side of the door
If it still does not work/move, then you have a bad door lock and it has to be replaced. Perhaps you may have to replace one door lock. But you still have to clean and re-lube the other 3.
Tino