91 560 sel with 255k. On the driver's side passenger door as it opened we heard a snap and after that the door only opens about halfway. What may have happened and the procedure to check it out and repair?

probably the door check has given up the ghost. they sezize up and the detent balls jam in the holes. Its a yellow metal tongue about 1/3 up from the bottom of the door on the huinge side. You'll need to remove the pin that anchors it to the chassis, open the door wide and remove the screws hiolding the unit in place inside the door. iirc there are two screws holding top and bottom plus another one behind the door panel.

don't try and force it, they can jam open which is kinda incovenient if you're not at home when it happens.

good luck

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1987 300e manual 250,000 km (sold)

hope you don't damage the door shell...we have a W140 sedan in the shop now that the door check came apart and punched an "outie" in the door skin, twisted the front window track, and the glass fell in the door and broke. I have seen a few that the door check damages the door shell where it goes into the shell, and the door needs to be replaced. On this 140, the bill for fixing the door and replacing all the damaged items, with an aftermarket glass (thanks to Allstate) is around $1750.

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2002 Ford ZX2
2 x 2013 Honda Civics