Sounds like a bad vac. pump. Disconnect the 19mm vacuum fitting at the brake booster and with the car running plug the hole with your thumb. You should fool a moderate/strong suction. Do this with all lines disconnected from the main vac pipe and all the nipples plugged. A vacuum gauge is also a good thing to buy if you own a w123.


The yellow lines with stripes are the door element lines. Green striped line is your climate control which leaks just as often as doors.

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1981 300SD 512k OM603