I've been having trouble lately locking and unlocking the my car with the key. It sometimes feels like I don't have it in the right position and I sometimes have to turn the key hard enough that I fear breaking it. Time for a new handle assembly? What about matching the key to the new tumbler?

And while I have a live thread: I think I need new injectors. I can hear nailing under certain loads and engine speeds. It's worse when the engines cold. I listened to the hot injectors with a stethoscope and couldn't hear anythin obviously bad. I can't hear nailing while it idles. I'm planning on getting my injectors rebuilt soon, anyway, but I'd like some advice. Where can I get the Monark nozzles?

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

Take the vac lock system offline and try the locks then.
Have your injectors tested, you may not need new nozzles.

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83 SD

84 CD

How do I take the lock system offline? just pull off the vac lines?

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

Try some graphite powder on the key and inside the keyhole before you start replacing whole assemblies.

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'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

The vacuum system should not affect the driver's door lock, it does not have an actuator and there is no way the master switch is going to prevent the key from turning. You have a mechanical problem with the lock/cylinder.

Yeah, release vacuum to the door lock system by unplugging the rubber lines at the yellow check valve under hood, I would think. The main vac pump keeps the reservoir filled, so it does come into play.
Here are a few attachments that may make sense.
You may have a mechanical problem and even MB says to use graphite, but locksmiths will tell you to use the liquid spray lube of your choice. Do this first, much quicker.

Attached Thumbnails

         

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83 SD

84 CD

I had a similar issue ... ended up removing and disassembling the lock cylinder ... there's some great pictures at the end of my thread. Need a little door lock diagnostic help on 240D

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1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

The locks in both my 240's were stiff until I graphited them.
They work fine now even the pass side in my 82 which was completely stuck.. Just be gentle while turning and working the key until things loosen up.

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1981 240D 143k 4 spd manual -SOLD

2004 VW Jetta TDI 5 speed 300k -still driven daily

I didn't like the sound of graphite powder gumming things up, and that's what it looked like it bodhi's pictures, plus we didn't have any on hand. Shot some WD-40 in there, now works fine. I swear, WD-40 and duct tape, you can fix anything...

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

This is what a local locksmith recommends.
Post #6, sentence four.

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83 SD

84 CD

yeah, that's why I did it.

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1983 240D 3.0T 4-speed manual, now sold

1989 Subaru GL Wagon 5-speed Touring Edition

MB makes a lock cylinder grease (SchlieBzylinderfett - A 001 989 26 51). A one second shot into the lock, then work it in with the key. Wipe the key when done. Would have more holding power than WD40, which will evaporate and leave nothing behind, basically. Worked great for me in a driver door lock that wouldn't find center and release the key smoothly. YMMV.

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mjk

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)

On the Mercedes 001 989 26 51 (10?)

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'84 300SD sold
124.128

I did not know about that lock cylinder grease, I'll have to remember that.

I had to replace my ignition tumbler about a year ago... it had been hard to turn for a few weeks, then it stopped turning completely. I was able to get it going again with some WD-40, but it didn't occur to me to try to repair it. Once I was able to get it started I limped straight to johnhef's place for triage in the form of another tumbler he had lying around.

It worked out in the end though, as the ignition tumbler that jammed used a different key than the door and trunk locks, leading me to believe that it had been replaced by a PO with what was probably a junkyard tumber. So it gave me an excuse to picked up a tumbler from the dealer that matched the rest of the car!


All that aside, i've got a question for you guys- Whenever it becomes extremely cold around here (<25 deg F), i'll sometimes have trouble with the driver's side door lock, but if I give it a blast from the WD-40 I keep in my trunk it opens right up. I've always attributed this to water freezing in the lock (and have since replaced the cracked window seal that I thought was causing it). Did you see symptoms similar to mine leading up to the total failure of your door tumbler?

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-Brian

1984 300SD, 375XXX miles, Light Ivory w/ Palomino TEX

Keep in mind that it might not just be the tumbler...there is a large latch mechanism assembly in the door, that has what seems like a complex linkage setup that can easily bind/bend and cause the key to not turn...

I just recently had this problem with my 300CD...I bought an entire new door handle (includes brand new key and tumbler) from the MB Classic Center, and installed it, but my key still wouldn't turn! It ended up being a bent linkage in the door latch mechanism. It's cover was missing, and looked like it had been tampered with, which caused it to bend when the door was closed (probably slammed). Anyway, I'm still waiting on my replacement latch mechanism. I'll report back once I install it.

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Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles