These have been repaired before. You can epoxy a piece of metal inside the plastic neck. Measure the I.D. and get some copper or aluminum pipe with an O.D. the matches the I.D.

Overflow nipple http://www.benzworld.org/forums/w123-e-ce-d-cd-td/1475276-broken-radiator-overflow-nipple-repair.html

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1999 E300DT (131,800) 154,000 Black on Black SOLD

2006 CLK 500 coupe Capri Blue on Grey (zoom,zoom)
47,000mi

04 VW TDI Passat 80,000mi
(Techno)

How to eliminate oil dependency through market-driven approaches.
“We could cut oil use in half by 2025, and by 2040, oil use could be zero,”
The Sound of Diesel Speed
Ode to MB