Years take a toll on rubber parts. Replacing the return line is a simple matter, just buy a section of rubber line, preferable cranckcase ventilation line (not heater hose) and instal it. On the 4.5 I used 19/32" vent line. The crankcase vent line is rated for petrochemical and can safely carry oils.
Two hose clamps and a section of line are all you need. Once installed you will have to refill and likely bleed the pump to ensure all air is out of the system.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.