Just wanted to share a little fix I did. I mainly followed the instructions here:
Door closing assist pump adjustment on S class
However, I did one thing a little different. I didn't mess with the spring because I personally disagree with this approach. All I had to do was put a little Ultra Black silicone gasket maker around the lip of the diaphragm and reassemble. Just smeared a thin layer on it, careful not to get any on the moving part of the diaphragm. If the diaphragm were torn I'd have tried the latex glove trick. So far this seems to have sealed it up and it works great. No further adjustment necessary.