For those not familiar with the terminology,
the door check is the strap that allows the mb door to stay in position when opened, and attaches to the jam of the door in the hinge area with a pin.
my 82 SD has been difficult to open the rear door since it got cold. it'd pop and complain, and not open all the way...
today, getting my daughter out, a nice dime bomber ball bearing shot across my floorboard... I'll get a pic of it when I find the sucker.
I looked over the check, and notice it has a small bend to the arm that attaches to the jam.
I've locked the door shut, and will not use it until I have a new check to install. I will take pics, and show DIY how to remove the door panel, and the check when I get it.
It's not a good idea to continue to use a door with a problematic check. they have been known to seize in the open position, and each time a sticking check is opened and closed, the thin sheetmetal that the arm is attached to flexes back and forth, and WILL result in cracked metal, and a rust point entry in your vehicle!
in a 140 general strap info

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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!