Trunk Lock Stuck - Central Locking Issue

[Lapis 635 Euro]

I have a new issue with my trunk lock on my '84 Euro 635 that from combing through the archives I could not find anyone else with a similar situation. Here are my symptoms:

°Trunk push button operates correctly and I can open the trunk no problem with the button.

°The keyhole for the trunk lock looks to be tilted slightly to the right of center, where it should be. See picture.

°Inserting the key in the trunk lock is difficult and only got easier by spraying PB Blaster into the key hole. Lots of crud has come out and I can insert the key now with some resistance but it does not want to turn at all. Afraid to apply pressure to turn and break the key off in the lock.

°With the trunk lid open I can see the latch move when using the push button.

°The door locks operate correctly with the key in the drivers side or passenger side doors. I think it is trying to activate the trunk lock with the central locking but the trunk lock does not move. The gas filler door locks/unlocks with the turn of the key in either door.

Any advice or further troubleshooting is welcomed.

[parkerbomar]

Push hard on the trunk below the logo while trying to unlock it. Also give it some firm hits with your fist. you might be able to get it back just enough to release.

I had this problem until I adjusted the lock properly.

[DesktopDave]

Just a guess, but I'm thinking the lock cylinder has a jammed pin. Give the PB Blaster a few days to do the job, hopefully it'll loosen up. Some gentle heat can also help, like a hair dryer. It'll encourage the PB into all the little nooks and crannies. You're right not to twist the key too hard, it's not too hard to break the tang off inside the lock. You'll really be up the creek.

The lock cylinders are zinc castings, pretty durable but subject to internal corrosion. I've seen a lot that are virtually welded together.

If you can't get the lock working at all after a day or two, you have other alternatives. BMW sold lock repair kits and services. It's been a while since I checked, and it wasn't cheap, but they could actually send you matched keys or cylinders based on VIN. Given that it's a Euro, your chances aren't great at dealer parts departments. A decent locksmith or indy mechanic can re-pin another E24 trunk release to match your keys.

Sometimes I prefer to take these parts out of the car, it's a lot easier on your back to have it out on the workbench. It's pretty easy to remove the entire lock assembly on most E24 - just two 10mm bolts hold it in. I think the later cars also have the power lock pushrod in a plastic retainer, it just pushes out. The trunk latch will still work...just push the latch release forward (into the trunk) to pop the lid.

[Lapis 635 Euro]

Push hard on the trunk below the logo while trying to unlock it. Also give it some firm hits with your fist. you might be able to get it back just enough to release.

I had this problem until I adjusted the lock properly.

Thanks for the tip! Was your trunk stuck locked shut? I am still able to open mine with the push button. Just trying to verify if you were striking the outside of the trunk lid or with the lid open above the lock.

- - - Updated - - -

Just a guess, but I'm thinking the lock cylinder has a jammed pin. Give the PB Blaster a few days to do the job, hopefully it'll loosen up. Some gentle heat can also help, like a hair dryer. It'll encourage the PB into all the little nooks and crannies. You're right not to twist the key too hard, it's not too hard to break the tang off inside the lock. You'll really be up the creek.

The lock cylinders are zinc castings, pretty durable but subject to internal corrosion. I've seen a lot that are virtually welded together.

If you can't get the lock working at all after a day or two, you have other alternatives. BMW sold lock repair kits and services. It's been a while since I checked, and it wasn't cheap, but they could actually send you matched keys or cylinders based on VIN. Given that it's a Euro, your chances aren't great at dealer parts departments. A decent locksmith or indy mechanic can re-pin another E24 trunk release to match your keys.

Sometimes I prefer to take these parts out of the car, it's a lot easier on your back to have it out on the workbench. It's pretty easy to remove the entire lock assembly on most E24 - just two 10mm bolts hold it in. I think the later cars also have the power lock pushrod in a plastic retainer, it just pushes out. The trunk latch will still work...just push the latch release forward (into the trunk) to pop the lid.

Very helpful, I agree with your assessment. I'll try to be patient with the PB as I don't notice any changes today when I tried again.

I do see the replacement lock/key set that BMW still offers, but would probably run into a wall getting them to recode it to my VIN with it being a Euro car as you said.

Can you give me a little more direction on how to remove the lock? I don't see the two 10mm bolts you referred to to remove the assembly. Thanks!

[SprCpe]

I'm sure it's not related but a couple comments. I had a similar problem with my drivers door lock, the cover was slightly off center. I was able to move it to center with a little flat screwdriver, that took care of that problem, then I decided the key was turning hard, I shot the lock full of PB penetrating oil, it clogged it up and I played hell cleaning it out. I talked to a locksmith I know, he chewed me out and said never use liquids in a lock, only use graphite. He may have just been BS'ing me but I've cleaned my locks and that's all I use on my cars and my home locks. Just some info.

[parkerbomar]

Ah I miss understood. if you can still get it open but it's not locking properly it most likely needs adjusting. Which is a kind of risky activity because you can shut the trunk and not be able to open it again if you do it wrong.

[Lapis 635 Euro]

Hooray! The lock freed up today and is now working again! I appreciate all the advice in this thread. I'm not sure if the PB Blaster finally worked its way through the tumbler or SprCpe's tip of using a little flat screwdriver that finally got it to move but I'm all good now. Hopefully this thread helps someone else if they end up in the same predicament.

[DesktopDave]

That's exactly what we wanted to hear, thanks for posting the update!

My spare set of locks had a cover plate completely fall off, I guess that's not as unusual as I thought it was.

[SprCpe]

Yahoo!!