I've got a vacuum leak in my 1980 300D, the engine won't shut off automatically some of the time and the climate control is kind of wacky right now, certainly not reliable. I picked this 300D up from a friend of mine for super cheap and I'm familiar with some cars but I've never had a mercedes before and really never messed with vacuum systems before either. I've got access to mitchell's on demand which covers 1983, but I haven't looked at it yet for the mercedes so I'm not sure how thorough it is and how much of a pain in the *** finding out where the leak is and solving it will be.

 

Buy a handheld vacuum pump and start testing lines to see which ones hold vacuum and/or operate their proper mechanisms. It's really not so tough, you just have to pay attention. There are a number of great online resources to help you trace lines.

 

chec your vacuum pump,make sure you have 23 or so on vacuum gauge.18 will not work.chec at brake booster.rebuild vacuum pump is an easy job,replace is pricey.if vacuum is good ,bloc off one area at a time to isolate leaks,use a golf T to block rubber hose.you cant judge if vacuum is good with your finger.you need a gauge.