Here's an old post
http://www.peachparts.com/shopforum/diesel-discussion/219024-82-240d-clutch-question.html my experience with my 83 240D clutch
Post was from 09, I had to read it to remember what I did. Some of it may apply to your's. There is a go/ no go gauge to check clutch thickness by where the clutch rod sits, though dimensions given for the gauge did not work for my clutch rod and had to be changed. Mine was also missing a shim (with a slot, which sits between the slave and the bell housing) which made using the gauge not possible. I had leaky steel lines (there are 2) and had to fix at least one of them with flaring tools. There were rusted fittings on the steel lines which made removal difficult. Replacing the clutch slave cyl and fixing the leaky lines cured my clutch problems.