I went through the drains last year in my 72. Starting from the front working towards the back: VERY important drain in the lowest area of the engine bay behind the headlight in front of the wheel well. Next in the cavity where the shock attaches to the fender, one on either side of the mounting point. Next in line are the drains in blower box area. (Small cover above the firewall) You have found the drains rocker panel and the gas door. As memory serves there is also a drain in the convertable top well, lowest point towards the hinge for the top. Finally take your spare tire out to find the drain in the trunk. As for cleaning techniques: I used a small extended length drill bit and worked it in by hand, then used a .22 caliber gun cleaning brush. I'm restoring this car so I did a POR 15 treatment afterward to stop any rust. If the areas are really dirty the best way to find the drain is with a cup of water. See where the water settles and you can be sure the Mercedes engineers put a drain there to get rid of it. After your done repeat the process with the water to see how good of a job you did. Anyone know of any drains I missed?

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BConrad