My car is an '87 Euro 300D, and the rear doors are difficult to fully open, mainly because they are rarely used. And they make a lot of niose while being opened.

I tried lubricating the guides, balls, and springs with good grease. It has improved a bit. But after a month, the doors are back to the same old "hard to open" condition.

Guys, it seem so simple, but I can't seem to fix it. How is this problem corrected?

I just did the same repair on my 300SD (1983).

It was so cheap to buy new parts - $16.00 per side. You should get new parts and install them - it's only 3 bolts and retaining clip.

Yes many W124's & W201's suffer from this problem. MB suggests lubricant with Molybdenum disulfide be sprayed directly on lock, w/outer door handle removed.

Problem is not on the door locks, but on the slide with spring loaded balls.

Slide is located near the door hinges, and it allows the door to index at either halfway or wide open position. It seems that the spring is too strong, but they're original.

Your problem is the door check straps.

On these parts there are early units and late units. The early units are MUCH better built units. If you want to do a good job with the repair, order the early units. It takes probably fifteen minutes per door to replace them. You will need to remove the door panel to replace them. You must be careful so as not to ruin the door panel. If you have not done this before, let us know and we'll tell you how to go about it.

Good luck,