My driver side door lock keeps freezing up, can't get the key in the keyhole I got it open with lock deicer, removed the door handle, soaked the tumbler in penetrating oil to clean it out, washed the oil out with brake clean and lubed it up with graphite lube. A week later, my door lock is frozen solid again. How can I prevent it getting full of water and doing this?

Silicone grease.

I have the same problem on my driver's door but not passenger door. Problem is a broken o-ring in the driver's door lock tumbler which keeps water out. A few things you can do:

1. Replace the o-ring (may not be easy to find the right size)

2. Replace the lock with one with a good o-ring

3. Install key less entry

4. Install a bra made from bicycle inner tube

I have done 3 and 4 and both work great in icing conditions but not 1 and 2 yet.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Every day in Maine is icing conditions... But that is a truly nifty solution, impressive! I'll to take it apart and see if I can find the o-ring you're talking about. If it's just a normal o-ring I might be able to find one at a parts store.

If you look on my door lock page, you'll find a photo of the cylinder removed about halfway through. You can see the o-ring clearly. If you want to take the lock down this far, you can easily change the o-ring, it's nothing special. It's also possible that the "door" that protects the lock from weather has lost it's spring.

http://www.coolcatcorp.com/Mercedes%20Locks/Door%20Lock/190%20Door%20Locks.html

That said, I think the problem may simply the accumulation of stuff inside the lock...including the junk you've been spraying in as well as dirt, water, sand, whatever. The problem with the advice you see here is that the lock cylinder is a dead end, so whatever you put into the lock stays there and adds to the problem. I think the best way to deal with this is to do a thorough disassembly and cleaning, and then spray it lightly with a dry silicone lube, which will repel water. And that's it. Graphite will accumulate and cause the lock to stick. Silicone grease will attract dirt.

That's a great link, thanks!
My little flap thing on the outside does work, I went through this same nonsense on a Subaru last year, that flap had stuck open letting water in.

I've already taken it apart and completely cleaned all the junk out that I sprayed in to get it open, lasted about a week then froze up again, so it must be that o-ring letting water in. I'll go seek out a new o-ring today and hopefully that'll be the end of my troubles!

IIRC, there are small magnetic circles you can put over the keyhole to prevent dew from accumulating in the lock.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

I think we been through this once before. The Mercedes locks are non magnetic.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Ahh. Tape then. I like the tube cover

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

2 solutions:

1) leave the doors open at all time.
2) Install Keyless remote control. Need an actuator for W123 or Gen 1 w126. Save all the lock cylinder's wear and tear. Personally, I would go this route, I did with the 83 300D and the 84 190D.

It is more trouble than it is worth to take the lock apart. Good luck.

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

I guess I could do that, I have a bunch of subaru door parts I could probably modify to fit, I even have subaru remotes and wireless receivers. I don't usually like carrying the remote fob around, but eh. I'm still gonna see if replacing that o-ring fixes the issue.

I also have issues with my trunk lock, but that's completely unrelated to the cold. I had to remove the latch assembly from the driver door to fix it, that was miserable. Removing the tailgate latch looks like utter hell, something I don't wanna deal with right now...

Well that was a massive pain in the ass, hopefully that's the end of my problems. If anyone thinks it's a good idea to disassemble a w123 door lock, it isn't.
Looks like the face of the lock, where the springy flap closes, is a bit bent??? Not sure how that happened, but it may not be sealing well and keeping water out.... We'll see.