To check you must take out the glove box and go in behind the center vents to pull off the vacuum hose and connect a gauge/pump to it. It isn't easy to replace. We get 3 hrs or so to do it. the book says to pull the dash pad to do it, but we don't.
1981 280GE SWB
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM