First, I read several things concerning a trunk release in the 1985 models. On a hunch, I removed the back seat and whadya know?? YES! This 1984 has a trunk release located under the rear seat!!!

So, I was able to open the trunk. Now that it is open, I went to press the lock release and it seems as though the mechanism won't fully pull back or disengage. I've turned the key CCW 45 degrees then back to horizontal, then removed the key. When I press on the lock as if I were going to unlock the trunk, the lock seems to "catch" or hit an slight obstruction.

If I push HARD, I can here and feel the lock going on in and appears to release (from what I can see while standing looking down on it). I'm thinking of using WD40 or I have Super Lube Dri Film Lubricant I bought from a locksmith. In addition are there are any adjustments I can make to the lock itself?

I've enclosed a photo though it may be difficult to see; any ideas are appreciated!!

Attached Thumbnails

 

Are you sure you're not using the valet key?

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I had a similar problem with my SDL when I got it. At some point, the striker had gotten slightly bent backwards towards the rear of the car. Went right in without hitting anything, but boy getting it open was a chore. The SDL also doesn't have the trunk release!

Bent it slightly back and kept repeating until I got it aligned perfectly. Closes with 1 finger and opens flawlessly with the pushbutton now.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

I'm using the regular key that unlocks the driver's door. It has a red dot on it; the trunk lid has been opening with no problems until this past Saturday.

It's not the striker in the trunk lid; it's the actual latch mechanism located in the body of the car just above the license plate. When I press in, it "catches" and is difficult to push all the way in.

note; updated the post; I'm thinking the latch mechanism is the problem.

Last evening, I went to check out the trunk lock again; VOILA! magically, it opens and closes like a brand new latch/tumbler!! Unsure why, though perhaps the Super Lube Dri Film worked its magic and managed to free things up. Gotta say, the Super Lube Dri Film lubricant may be a true "miracle in a can".

https://www.amazon.com/Super-Lube-11016-Aerosols-Dri-Film/dp/B000RFRM4U/ref=sr_1_2?ie=UTF8&qid=1493729429&sr=8-2&keywords=Super+Lube+Dri-film+lubricant