I have the owners manual and have read the bit about locking the trunk by turning the key 90 degrees to the right and removing it so that the valet key cannot open it. [I recently purchased the valet key from the dealer.]

I am not able to make the trunk lock cylinder turn this far. Glovebox locking in the same manner is no problem.

Question: Is the master key with the red dot a different key than the normal keys that will operate the ign, trunk, door, glovebox?

It seems that would make four:

flat normal key (for wallet)
plastic grip normal key
plastic grip valet key
plastic grip "red dot" master key

Anybody?

Thanks!

The red dot are the old keys, it was MB's way in the 80's of showing off the car had an alarm. The new ones don't have it.

Your lock is probably stuck, since hardly anyone ever uses that feature. Try some graphite powder in the lock.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Thanks, I will try that. I hate forcing things.

I would spray some pb blaster in there, let it soak for a day then spray brake cleaner in really well. get all traces of gunk out. then blow it out really dry with air, or co2 spray. gotta get all junk out, try the key then, if it's smooth, great, if not repeat above. once it's totally smooth, if you feel in necessary, put in some graphite powder to prevent future problems with wear.

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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 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

FWIW, my locksmith says not to use graphite. Use WD40.

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Charles
1983 300D, bought new, 215k+ miles, donated to Purple Hearts veterans charity but I have parts for sale: http://www.peachparts.com/shopforum/mercedes-benz-cars-sale/296386-fs-1-owner-83-mb-300d-turbo-rebuild-parts.html

Liquid's will attract dirt.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Mine too.

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83 SD

84 CD

my brother, a locksmith uses the saying "graphite is a locksmiths best friend" meaning it generates lots of business.
I learned that the hard way when I squirted Graphite in a new SAAB and a year later the lock jammed up. It gets into the pins and dries out and they stick.
I suggest WD40 or better yet, Tri-Flow spray on locks.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

The 90* turn works well on my SDL: It locks the truck shut with a deadbolt. The central locking still works the standard latch I believe, but the bolt holds the trunk shut.

-Jason

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

last time i tried to get a valet key the dealr said they are no longer available, i have one for my 1986 SDL, the valet key will not actually even turn the trunk lock and will not even enter the glove box key hole, the valet key is distinguished by an oval head

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1967 250 S
1967 280SE
1968 250S
1971 280 SE
1973 220
1974 280 S
1975 450 SEL
1976 220 D
1979 300SD
1983 300 SD
1985 230 TE euro
1986 280SL
1986 500 SEL euro
1986 190E 2.3
1990 300 SE
2003 C230 K
2004 C230 K
1987 560SEL
1987 300SDL now in canada
2005 C230
1998 C43 AMG Sold to DON
1993 190E 2.6
300TD Former daily driver Totaled
current:
R320 CDI
Ram 2500 Cummins

Any locksmith who recommends WD-40 is REALLY just looking for future business. This is the worst possible substance you can use on a moving part. It is designed so that the lubricating portion will offgas in a month or two leaving behind a gummy tar like substance. Fine for when you are wanting to waterproof something but horrible for moving parts.

At this point then people spray in more WD-40. The volatiles will temporarily dissove the tar, allowing the part to move. But when they evaporate you now have twice as much gum. After a year or two the lock is useless.

The best substance is plain light grade oil. But it will run over everything so keep napkins handy. Graphite is good for certain installations. It won't "dry out" (it is a powder, not a liquid) but does not have the rust prevention of oil.

There are plenty of locksmiths who don't know their rear end from a hole in the ground as you can see from reading the above posts.

The best product I've found for lock lubrication is a good spray oil like Mr. Moly spray grease with a MoS2 in tenacious oil.

The easiest available decent-quality spray oil is IMO 1-Lube from the people I otherwise despise: the Slick-50 guys (ironic, isn't it). 1-Lube is a good tenacious oil in a spray can, might have some Teflone/PTFE in it (don't remember), and unlike WD-40 (AKA: starting fluid) the oil sticks around. I use it in my shop on production parts, available at Menard's and other places.

True IMO that graphite has the ability to get into locks, impact the void behind the tumblers, and make the lock inoperable.

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Gone to the dark side

- Jeff

I don't own a can of WD40, I still can't find something its good for. Well other than attracting fish.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

All fixed -- it was the sliding bolt to the left of the latch. I lubricated it and the part on the lid that it passes through. Thanks everyone for the info!

I was using 350cs silicone oil with a fugitive carrier.